Imaging lens

ABSTRACT

The present invention is an imaging lens of which optical performance does not deteriorate even in a high temperature environment, various aberrations are well corrected, optical length is short, and back focus is sufficiently secured, the imaging lens comprising a first junction type compound lens, an aperture stop S, a second junction type compound lens, and a third junction type compound lens, which are arranged in this sequence from an object side to an image side. The first junction type compound lens comprises a first lens L 1 , a second lens L 2  and a third lens L 3  arranged in this sequence from the object side to the image side, the second junction type compound lens comprises a fourth lens L 4 , a fifth lens L 5  and a sixth lens L 6  arranged in this sequence from the object side to the image side, and the third junction type compound lens comprises a seventh lens L 7 , an eighth lens L 8  and a ninth lens L 9  arranged in this sequence from the object side to the image side. The first lens, the third lens, the fourth lens, the sixth lens, the seventh lens and the ninth lens are formed of a curable resin material, and the second lens, the fifth lens and the eighth lens are formed of a high softening temperature optical glass material.

TECHNICAL FIELD

The present invention relates to an imaging lens, and more particularlyto an imaging lens that can be suitably mounted on a portable telephoneor the like.

BACKGROUND ART

In a portable telephone with a built-in digital camera, an imaging lensis mounted on a printed circuit board. As a method for mounting animaging lens on a printed circuit board, a reflow soldering processingis used. Hereafter the reflow soldering may simply be called “reflow”.Reflow processing is a method for soldering an electronic component on aprinted circuit board, by placing a solder ball in advance at a locationwhere an electronic component is connected, placing the electroniccomponent there, heating to melt the solder ball, then cooling thesolder down.

Generally in mass production steps, a reflow step for performing reflowprocessing is used as a method for mounting electronic elements or suchcomponents as an imaging lens on a printed circuit board. If the reflowstep is used, the mounting cost of components on a printed circuit boardcan be decreased, and manufacturing quality can be maintained at apredetermined level.

In the reflow step of the manufacturing steps of a portable telephonecomprising an imaging lens, not only are electronic components arrangedat predetermined positions on a printed circuit board, but also theimaging lens itself or a socket for installing the imaging lens isdisposed on the printed circuit board.

The imaging lens installed in portable telephones are largely made ofplastic in order to decrease the manufacturing cost, and to insure lensperformance. Therefore a heat resistant socket component is used forinstalling an imaging lens in order to prevent thermal deformation ofthe imaging lens in a high temperature environment, which makes itimpossible to maintain optical performance thereof.

In other words, in the reflow step, a heat resistant socket componentfor installing an imaging lens is mounted on the printed circuit boardof the portable telephone, so that the imaging lens is not exposed tohigh temperature in the reflow step (e.g. see Patent Documents 1 to 3).However, using a heat resistant socket component for installing animaging lens makes the manufacturing steps complicated, and increasesthe manufacturing cost, including the cost of this heat resistantsocket.

A recent demand is that the optical performance of an imaging lensinstalled in a portable telephone does not deteriorate even if theportable telephone itself is placed in about a 150° C. high temperatureenvironment, considering the case of the portable telephone being leftin an automobile which temporarily becomes a high temperatureenvironment. A conventional imaging lens made of plastic material cannotmeet this demand.

In order to implement an imaging lens of which optical performance ismaintained even in a high temperature environment, forming an imaginglens using a high softening temperature mold glass material is possible(e.g. see Patent Document 4). Since the temperature at which the highsoftening temperature mold glass material softens is several hundreddegrees or more, the deterioration of optical performance of an imaginglens in a high temperature environment can be avoided, but at themoment, an imaging lens made of mold glass material is not very popular,because the manufacturing cost is very high.

In addition to the above mentioned thermal characteristics, an imaginglens installed in a portable telephone must satisfy the followingconditions related to optical characteristics. One condition is that theoptical length is short. The optical length refers to a distance from anentrance plane at an object side to an image formation plane (alsocalled “image sensing plane”) of the imaging lens. In other words, whena lens is designed, the ratio of the optical length to the compositefocal distance of the imaging lens must be minimized. In the case of aportable telephone, for example, this optical length must at least beshorter than the thickness of the portable telephone unit.

On the other hand, a back focus, which is defined as a distance from theoutgoing plane at the image side to the image sensing plane of theimaging lens, should be as long as possible. In other words, when thelens is designed, the ratio of the back focus to the focal distance mustbe maximized. This is because such components as a filter and a coverglass must be inserted between the imaging lens and the image sensingplane.

In addition to this, it is naturally demanded for the imaging lens thatvarious aberrations are corrected to be small enough that the distortionof the image is not visually recognized, and that the integrationdensity of the image sensing elements in minimal units (also called“pixels”), which are arranged in a matrix on the light receiving planeof a CCD (Charge Coupled Device) image sensor, is sufficientlysatisfied. In other words, various aberrations of the imaging lens mustbe well corrected. Hereafter an image, of which various aberrations arewell corrected, may be called a “good image”.

Patent Document 1: Japanese Patent Application Laid-Open No. 2006-121079(Patent No. 3799615)

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-328474(Patent No. 3915733)

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-063787(Patent No. 3755149)

Patent Document 4: Japanese Patent Application Laid-Open No. 2005-067999

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

With the foregoing in view, it is an object of the present invention toprovide an imaging lens suitable for being installed in a portabletelephone, and of which heat resistance is guaranteed and opticalperformances does not deteriorate, even in a high temperatureenvironment of a reflow step, or even if the imaging lens is installedin a portable telephone and is temporarily placed in the highesttemperature environment in the design specifications.

It is another object of the present invention to provide an imaging lensof which optical length is short enough to be installed in a portabletelephone, back focus is long enough to insert such a component as afilter and a cover glass between the imaging lens and the image sensingplane, and with which a good image is acquired.

Means for Solving the Problems

To achieve the above objects, a first imaging lens of this inventioncomprises a first junction type compound lens, an aperture stop, asecond junction type compound lens, and a third junction type compoundlens, characterized in that the first junction type compound lens, theaperture stop, the second junction type compound lens, and the thirdjunction type compound lens are arranged in this sequence from an objectside to an image side.

The first junction type compound lens comprises a first lens, a secondlens and a third lens arranged in this sequence from the object side tothe image side, and the second junction type compound lens comprises afourth lens, a fifth lens and a sixth lens arranged in this sequencefrom the object side to the image side, and the third junction typecompound lens comprises a seventh lens, an eighth lens and a ninth lensarranged in this sequence from the object side to the image side.

The first lens, the third lens, the fourth lens, the sixth lens, theseventh lens and the ninth lens are formed of a curable resin material,and the second lens, the fifth lens and the eighth lens are formed of ahigh softening temperature optical glass material. The first lens andthe second lens are indirectly bonded, the second lens and the thirdlens are indirectly bonded, the fourth and the fifth lens are indirectlybonded, the fifth lens and the sixth lens are indirectly bonded, theseventh lens and the eighth lens are indirectly bonded, and the eighthlens and the ninth lens are indirectly bonded.

Or the first lens, the second lens, the third lens, the fourth lens, thefifth lens, the sixth lens, the seventh lens, the eighth lens and theninth lens are formed of a curable resin material. The first lens andthe second lens are directly bonded or indirectly bonded, the secondlens and the third lens are directly bonded or indirectly bonded, thefourth lens and the fifth lens are directly bonded or indirectly bonded,the fifth lens and the sixth lens are directly bonded or indirectlybonded, the seventh lens and the eighth lens are indirectly bonded, andthe eighth lens and the ninth lens are directly bonded or indirectlybonded.

A second imaging lens of the present invention comprises an aperturestop (first stop), a first junction type compound lens, a second stop, asecond junction type compound lens and a third junction type compoundlens, characterized in that the aperture stop (first stop), the firstjunction type compound lens, the second stop, the second junction typecompound lens and the third junction type compound lens are arranged inthis sequence from an object side to an image side.

The first junction type compound lens comprises a first lens, a secondlens, and a third lens arranged in this sequence from the object side tothe image side, the second junction type compound lens comprises afourth lens, a fifth lens and a sixth lens arranged in this sequencefrom the object side to the image side, and the third junction typecompound lens comprises a seventh lens, an eighth lens and a ninth lensarranged in this sequence from the object side to the image side.

The first lens, the third lens, the fourth lens, the sixth lens, theseventh lens and the ninth lens are formed of a curable resin material,and the second lens, the fifth lens and the eighth lens are formed of ahigh softening temperature optical glass material. The first lens andthe second lens are indirectly bonded, the second lens and the thirdlens are indirectly bonded, the fourth lens and the fifth lens areindirectly bonded, the fifth lens and the sixth lens are indirectlybonded, the seventh lens and the eighth lens are indirectly bonded, andthe eighth lens and the ninth lens are indirectly bonded.

The curable resin material refers to both a thermosetting resin materialand a UV-curable resin material. The high softening temperature opticalglass material refers to such optical glass material as a high softeningtemperature mold glass material or boro-silicate glass.

Bonding in the case when the second lens, the fifth lens and the eighthlens are formed of a curable resin material will be described. In thedescription, the first junction type compound lens is used as anexample. The cases of the second and third junction type compound lensesare also the same, so description thereof is omitted.

The bonding of the second lens formed of a curable resin material andthe first lens or the third lens formed of a curable resin material isimplemented as follows. A liquid type curable resin material iscontacted to the second lens formed of the curable resin material, andthe first lens or the third lens is bonded to the second lens bysolidifying, that is by curing, this curable resin material. Thisbonding may be called “direct bonding” herein below. The second lens andthe first lens or the third lens may be bonded by using an adhesivebetween the second lens and the first lens or the third lens. Thisbonding may be called “indirect bonding” herein below.

The bonding of the second lens formed of a high Softening temperatureoptical glass and the first lens or the third lens formed of a curableresin material, on the other hand, is performed by indirect bonding.

When the junction type compound lens is implemented by indirect bonding,whether it is the case of the second lens formed of a curable resinmaterial or the case of the second lens formed of a high softeningtemperature optical glass, the reflection in the interface between thesecond lens and the first lens or the third lens can be decreased if theadhesive is selected so that the optical characteristics of the adhesivecan be utilized, such as selecting an appropriate refractive index ofthe adhesive with respect to the refractive index of the second lens andthe refractive index of the first or third lens.

If the coating processing is performed on the surface of the second lensfacing the first lens or the third lens, and these lenses are bonded,whether adhesive is used to bond or not, the reflection in the interfacewith the first lens (or the third lens) can be decreased.

In the above mentioned first or second imaging lens, it is preferable toset settings so as to satisfy the following Conditions (1) to (12).0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦ν₂−ν₁|≦30.0  (3)0≦ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12)where

N₁: refractive index of the first lens

N₂: refractive index of the second lens

N₃: refractive index of the third lens

ν₁: Abbe number of the first lens

ν₂: Abbe number of the second lens

ν₃: Abbe number of the third lens

N₄: refractive index of the fourth lens

N₅: refractive index of the fifth lens

N₆: refractive index of the sixth lens

ν₄: Abbe number of the fourth lens

ν₅: Abbe number of the fifth lens

ν₆: Abbe number of the sixth lens

N₇: refractive index of the seventh lens

N₈: refractive index of the eighth lens

N₉: refractive index of the ninth lens

ν₇: Abbe number of the seventh lens

ν₈: Abbe number of the eighth lens

ν₉: Abbe number of the ninth lens

The shapes of the first to the ninth lenses of the above mentioned firstand second imaging lenses are as follows.

The second lens, the fifth lens and the eighth lens can beoptical-parallel plates. An optical-parallel plate normally is notreferred to as a lens, but to simplify description, the optical-parallelplate may be included in a lens description, regarding this as a specialcase where the radius of curvature of the lens surface is infinite.

If the second lens, the fifth lens and the eighth lens areoptical-parallel plates, the first lens can be a plano-convex lens wherethe object side face of the first lens is a convex surface facing theobject side on a paraxial line, the third lens can be a plano-concavelens where the image side face of the third lens is a concave surfacefacing the image side on a paraxial line, the fourth lens can be aplano-concave lens where the object side face of the fourth lens is aconcave surface facing the object side on a paraxial line, the sixthlens can be a plano-convex lens where the image side face of the sixthlens is a convex surface facing the image side on a paraxial line, theseventh lens can be a plano-convex lens where the object side face ofthe seventh lens is a convex surface facing the object side on aparaxial line, and the ninth lens can be a plano-concave lens where theimage side face of the ninth lens is a concave surface facing the imageside on a paraxial line.

The following is also possible if the second lens, the fifth lens andthe eighth lens are optical-parallel plates. In other words, the firstlens can be a plano-convex lens where the object side face of the firstlens is a convex surface facing the object side on a parallel line, thethird lens can be a plano-convex lens where the image side face of thethird lens is a convex surface facing the image side on a paraxial line,the fourth lens can be a plano-concave lens where the object side faceof the fourth lens is a concave surface facing the object side on aparaxial line, the sixth lens can be a plano-convex lens where the imageside face of the sixth lens is a convex surface facing the image side ona paraxial line, the seventh lens can be a plano-convex lens where theobject side face of the seventh lens is a convex surface facing theobject side, and the ninth lens can be a plano-concave lens where theimage side face of the ninth lens is a concave surface facing the imageside on a paraxial line.

It is also possible that the second lens is a meniscus lens of whichconvex surface facing the object side, the first lens is a lens wherethe object side face of the first lens is a convex surface facing theobject side on a paraxial line, the third lens is a lens where the imageside face of the third lens is a concave surface facing the image sideon a paraxial line, the fifth lens is a meniscus lens of which convexsurface faces the image side, the fourth lens is a lens where the objectside face of the fourth lens is a concave surface facing the object sideon a paraxial line, the sixth lens is a lens where the image side faceof the sixth lens is a convex surface facing the image side on aparaxial line, the eighth lens is a biconvex lens of which both sidefaces are convex surfaces, the seventh lens is a lens where the objectside face of the seventh lens is a convex surface facing the object sideon a paraxial line, and the ninth lens is a lens where the image sideface of the ninth lens is a concave surface facing the image side on aparaxial line.

It is also possible that the second lens is a biconvex lens of whichboth side faces are convex surfaces, the first lens is a lens where theobject side face of the first lens is a convex surface facing the objectside on a paraxial line, the third lens is a lens where the image sideface of the third lens is a convex surface facing the image side on aparaxial line, the fifth lens is a meniscus lens of which convex surfacefaces the image side, the fourth lens is a lens where the object sideface of the fourth lens is a concave surface facing the object side on aparaxial line, the sixth lens is a lens where the image side face of thesixth lens is a convex surface facing the image side on a paraxial line,the eighth lens is a meniscus lens of which convex surface faces theimage side, the seventh lens is a lens where the object side face of theseventh lens is a convex surface facing the object side on a paraxialline, and the ninth lens is a lens where the image side face of theninth lens is a concave surface facing the image side on a paraxialline.

As mentioned above, the second lens, the fifth lens and the eighth lenscan be an optical-parallel plate, meniscus lens or biconvex lens, but isnot limited to these, but may be a concave lens, for example. The shapesof the second lens, the fifth lens and the eighth lens are determined byconvenience in forming the first lens and third lens, the fourth lensand sixth lens, and the seventh lens and ninth lens, which are resinlenses formed on both sides of a respective lens, or by convenience indesigning the imaging lens of the present invention.

In other words, if the second lens, the fifth lens and the eighth lensare implemented by a lens constructed by a curved surface, such as ameniscus lens, a convex lens or a concave lens, the bonding surface witha resin lens, which is formed on both sides of the second lens, fifthlens and eighth lens respectively, becomes wider compared with the caseof implementing the lens by an optical-parallel plate, and bondingstrength increases accordingly. Also the range of choices of the radiusof curvature of the second lens, fifth lens and eighth lens, which is adesign parameter to implement performance of the lens, includingaberration, becomes wider, which makes designing of the imaging lens ofthis invention easier.

On the other hand, it becomes more difficult to prevent the entry ofbubbles into the bonding interface when junction type compound lenses(the first, second and third junction type compound lenses) isfabricated, if the radius of curvature of the second lens, fifth lensand eighth lens is decreased (that is, if curvature thereof isincreased). Also using such lens with a curved surface as a meniscuslens instead of an optical-parallel plate for the second lens, fifthlens and eighth lens, increases the manufacturing cost, compared withthe case of using an optical-parallel plate.

To form the first and second imaging lenses of the present invention, itis preferable that the object side face of the first lens, the imageside face of the third lens, the object side face of the fourth lens,the image side face of the sixth lens, the object side face of theseventh lens and the image side face of the ninth lens are aspherical.

It is also preferable that at least one surface out of both surfaces ofthe second lens, both surfaces of the fifth lens, and both surfaces ofthe eighth lens, a total of six surfaces, is coating-processed, thefirst lens and the second lens are indirectly bonded, the second lensand the third lens are indirectly bonded, the fourth lens and the fifthlens are indirectly bonded, the fifth lens and the sixth lens areindirectly bonded, the seventh lens and the eighth lens are indirectlybonded, and the eighth lens and the ninth lens are indirectly bonded.

To form the first and second imaging lenses of the present invention, itis preferable that the curable resin material, which is a material ofthe first lens, third lens, fourth lens, sixth lens, seventh lens andninth lens, is a transparent curable silicone resin. “Transparent” hereindicates that the light absorption of visible light is small(transparent) enough to have no influence on practical use.

EFFECT OF THE INVENTION

According to the first and second imaging lenses of the presentinvention, in the first junction type compound lens constituting theimaging lenses, the first and the third lenses, which are formed of acurable resin material, sandwich and are indirectly bonded to the secondlens, which is formed of a high softening temperature optical glassmaterial. In the second junction type compound lens, the fourth and thesixth lenses, which are formed of a curable resin material, sandwich andare indirectly bonded to the fifth lens, which is formed of a highsoftening temperature optical glass material. And in the third junctiontype compound lens, the seventh and the ninth lenses, which are formedof a curable resin material, sandwich and are indirectly bonded to theeighth lens, which is formed of a high softening temperature opticalglass material.

In the first imaging lens of the present invention, the first junctiontype compound lens may be comprised of the first lens, the second lensand the third lens arranged in this sequence from the object side to theimage side, where the first lens, the second lens and the third lens areformed of a curable resin material. The second junction type compoundlens may be comprised of the fourth lens, the fifth lens and the sixthlens arranged in this sequence from the object side to the image side,where the fourth lens, the fifth lens and the sixth lens are formed of acurable resin material. And the third junction type compound lens may becomprised of the seventh lens, the eighth lens and the ninth lensarranged in this sequence from the object side to the image side, wherethe seventh lens, the eighth lens and the ninth lens are formed of acurable resin material. In this case, the first lens and the second lensare directly bonded or indirectly bonded, and the second lens and thethird lens are directly bonded or indirectly bonded. The fourth lens andthe fifth lens are directly bonded or indirectly bonded, and the fifthlens and the sixth lens are directly bonded or indirectly bonded. Theseventh lens and the eighth lens are directly bonded or indirectlybonded, and the eighth lens and the ninth lens are directly bonded orindirectly bonded.

The high softening temperature optical glass material here refers to anoptical glass material of which softening temperature is higher thanboth the temperature of reflow processing and the maximum environmentaltemperature in the design specifications of the junction type compoundlens. In the following description, the phrase “high softeningtemperature optical glass material” is used when a thermalcharacteristic of the optical glass material is discussed, and thesimple phrase “optical glass material” may be used when an opticalcharacteristic is discussed.

The curable resin material does not soften once curing processing isperformed, even if the temperature rises more than a predeterminedtemperature. This nature of the curable resin material is different fromthe nature of a plastic resin material, such as plastic material, whichbecomes soft and plasticized if the material is exposed to a temperaturethat exceeds a predetermined temperature, which is referred to as a“softening temperature” (also referred to as a “glass transitiontemperature”). In other words, once curing processing is performed andmaterial solidifies, the geometric shape of the curable resin materialdoes not change.

Therefore the geometric shapes of the first lens, the third lens, thefourth lens, the sixth lens, the seventh lens and the ninth lens do notchange, and optical performance thereof does not deteriorate even if thelenses are placed in a high temperature environment. The second lens,the fifth lens and the eighth lens are also formed of a high softeningtemperature optical glass material, so the optical performance thereofdoes not deteriorate even under a high temperature environment. In thecase of the second lens, the fifth lens and the eighth lens formed of acurable resin material as well, the optical performance thereof does notdeteriorate even under a high temperature environment. The hightemperature environment here refers to a temperature environment higherthan both the temperature in reflow processing and the maximumtemperature in the design specifications of the junction type compoundlens.

Therefore the optical performance of the first junction type compoundlens, the second junction type compound lens and the third junction typecompound lens is guaranteed even in a high temperature environment,where the temperature is at the maximum, that is assumed in reflowprocessing and when the imaging lens is in use.

If the second lens, the fifth lens and the eighth lens are formed usinga curable resin material, the following effect can be implemented.Compared with the case of forming these lenses using a high softeningtemperature optical glass material, the manufacturing accuracy of thethickness of the second lens, the fifth lens and the eighth lens ishigh. In other words, the manufacturing accuracy of the thickness of thesecond lens, the fifth lens and the eighth lens, in the case of using ahigh softening temperature optical glass material, is about ±10 μm,while the manufacturing accuracy of the thickness thereof, in the caseof using a curable resin material, can be improved up to about ±3 μm. Inthis way, since the manufacturing accuracy of the thickness of thesecond lens, the fifth lens and the eighth lens can be increased, theimaging lens can be manufactured without deviating very much fromvarious characteristics, such as aberration, that are assumed in designspecifications.

In order to implement the above mentioned indirect bonding, an adhesiveis used between the bonding surfaces. When the junction type compoundlens is manufactured by indirect bonding, the first lens to the thirdlens are formed first, then an adhesive is coated on a surface of thesecond lens facing the first lens or the third lens, or on the surfaceof the first lens or the third lens facing the second lens, and bothlenses are contacted. In the same way, the fourth lens to the sixth lensare formed first, then an adhesive is coated on a surface of the fifthlens facing the fourth lens or sixth lens, or on the surface of thefourth lens or sixth lens facing the fifth lens, and both lenses arecontacted. In the same way, the seventh lens to the ninth lens areformed first, then an adhesive is coated on a surface of the eighth lensfacing the seventh lens or ninth lens, or on the surface of the seventhlens or ninth lens facing the eighth lens, and both lenses arecontacted.

Coating processing may be performed on a surface of the second lensfacing the first lens or the third lens, and both lenses are indirectlybonded. Coating processing may be performed on a surface of the fifthlens facing the fourth lens or the sixth lens, and both lenses areindirectly bonded. Coating processing may be performed on the surface ofthe eighth lens facing the seventh lens or the ninth lens, and bothlenses are indirectly bonded.

When indirect bonding is implemented, reflection in the interfacebetween the second lens and the first lens or the third lens can bedecreased if adhesive is selected so that the optical characteristics ofthe adhesive is utilized, such as selecting an appropriate refractiveindex of the adhesive with respect to the refractive index of theoptical glass and the refractive index of the curable resin material. Inthe same way, the reflection in the interface between the fifth lens andthe fourth lens or the sixth lens can be decreased. In the same way, thereflection in the interface between the eighth lens and the seventh lensor the ninth lens can be decreased. If the coating processing isperformed on the surface of the second lens facing the first lens or thethird lens, and these lenses are bonded, as mentioned above, thereflection in the interface with the first lens (or the third lens) canbe decreased. In the same way, if coating processing is performed on thesurface of the fifth lens facing the fourth lens or the sixth lens, andthese lenses are bonded, as mentioned above, the reflection in theinterface with the fourth lens (or the sixth lens) can be decreased. Inthe same way, if coating processing is performed on the surface of theeighth lens facing the seventh lens or the ninth lens, and these lensesare bonded, as mentioned above, the reflection in the interface with theseventh lens (or the ninth lens) can be decreased.

Now the optical characteristics of the imaging lens of the presentinvention will be described.

The optical structural principle of the imaging lens of the presentinvention implements two roles, which are aberration correction andimage formation, by single junction type compound lenses, of whichoptical characteristics, such as the refractive index, are as uniform aspossible. In other words, it is preferable that the respectiverefractive indexes and the Abbes number of the first to third lensesconstituting the first junction type compound lens of the imaging lensof the present invention do not differ very much from each other. Alsoit is preferable that the respective refractive indexes and the Abbenumbers of the fourth to sixth lenses, constituting the second junctiontype compound lens, do not differ very much from each other. Also it ispreferable that the respective refractive indexes and the Abbe numbersof the seventh to ninth lenses, constituting the third junction typecompound lens, do not differ very much from each other.

This means that it is ideal that the respective refractive indexes andthe Abbe numbers of the first to third lenses, the fourth to sixthlenses and the seventh to ninth lenses are the same as each other. Inpractical terms, however, it is extremely difficult to find acombination of an optical glass material and a curable resin materialwith which refractive indexes and Abbe numbers are precisely the same.

Therefore the inventor of the present invention checked, through varioussimulations and prototyping, the differences of the refractive indexesand the Abbe numbers between the optical glass material and the curableresin material constituting the first, second and third junction typecompound lenses respectively, which could generated good images. As aresult, it was confirmed that good images can be acquired byconstructing an imaging lens which satisfies the above Conditions (1) to(12).

In other words, if the difference between the refractive index N₁ of thefirst lens and the refractive index N₂ of the second lens, thedifference between the refractive index N₂ of the second lens and therefractive index N₃ of the third lens, the difference between therefractive index N₄ of the fourth lens and the refractive index N₅ ofthe fifth lens, the difference between the refractive index N₅ of thefifth lens and the refractive index N₆ of the sixth lens, the differencebetween the refractive index N₇ of the seventh lens and the refractiveindex N₈ of the eighth lens, and the difference between the refractiveindex N₈ of the eighth lens and the refractive index N₉ of the ninthlens are within 0.1 respectively, then the distortion aberration,astigmatism aberration and chromatic/spherical aberration become smallenough to generate good images.

Also if the difference between the Abbe number ν₁ of the first lens andthe Abbe number ν₂ of the second lens, the difference between the Abbenumber ν₂ of the second lens and the Abbe number ν₃ of the third lens,the difference between the Abbe number ν₄ of the fourth lens and theAbbe number ν₅ of the fifth lens, the difference between the Abbe numberν₅ of the fifth lens and the Abbe number ν₆ of the sixth lens, thedifference between the Abbe number ν₇ of the seventh lens and the Abbenumber ν₈ of the eight lens, and the difference between the Abbe numberν₈ of the eighth lens and the Abbe number ν₉ of the ninth lens arewithin 30.0 respectively, then the value of the chromatic aberration canbe small enough to generate good images, and the images can havesufficient contrast.

Moreover, as the following examples show, if the above Conditions (1) to(12) are satisfied, an imaging lens of which optical length is shortenough to be installed in a portable telephone, of which back focus islong enough to insert such components as a filter and cover glassbetween the imaging lens and the image sensing plane, and with whichgood images can be acquired, can be implemented.

The first imaging lens of the present invention is characterized in thatthe aperture stop to define the entrance pupil is disposed between thefirst junction type compound lens and the second junction type compoundlens. Hence the aperture stop has a function to remove a flare which isgenerated in the first junction type compound lens.

The second imaging lens of the present invention is characterized inthat the aperture stop (first stop) to define the entrance pupil isdisposed on the front face of the first junction type compound lens,that is, the object side of the first junction type compound lens. Hencethe entrance pupil can be disposed closer to the object side, and theprincipal ray can be entered at an angle close to vertical to the imagesurface, and the generation of shading can be prevented. Therefore inthe second imaging lens, the entrance pupil diameter can be set to belarge, and a lens with a small F number, that is, a bright lens, can beimplemented. As the later described embodiments show, the F numbers ofthe imaging lenses shown in Embodiments 2, 3 and 5, which areembodiments of the second imaging lens, are smaller than the F numbersof the imaging lenses shown in Embodiments 1 and 4, which areembodiments of the first imaging lens.

The first imaging lens, on the other hand, has a characteristic in whichthe F number can be easily changed in the manufacturing process. Inother words, the size of the aperture stop is changed to change the Fnumber of the imaging lens, and in the case of the first imaging lenswhere the aperture stop is disposed between the first junction typecompound lens and the second junction compound lens, the F number can bechanged simply by replacing the aperture stop.

But if the aperture stop is disposed on the front face of the firstjunction type compound lens, just like the case of the second imaginglens, the size of the aperture must be set in the stage of fabricating abarrel to secure the first to third junction type compound lensesconstituting the imaging lens, so that the tip of the barrel plays arole of the aperture stop. In other words, every time the F number ischanged, the barrel of the imaging lens must be redesigned, and the dieto fabricate the barrel of the imaging lens must be recreated.

As described above, the first imaging lens and the second imaging lenshave different characteristics. The imaging lens to be used is a matterof choice depending on an object to which the imaging lens is applied(e.g. portable telephone, digital camera).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view depicting a first imaging lensaccording to the present invention;

FIG. 2 is a cross-sectional view depicting an imaging lens according toEmbodiment 1;

FIG. 3 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 1;

FIG. 4 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 1;

FIG. 5 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 1;

FIG. 6 is a cross-sectional view depicting a second imaging lensaccording to the present invention;

FIG. 7 is a cross-sectional view depicting an imaging lens according toEmbodiment 2;

FIG. 8 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 2;

FIG. 9 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 2;

FIG. 10 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 2;

FIG. 11 is a cross-sectional view depicting an imaging lens according toEmbodiment 3;

FIG. 12 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 3;

FIG. 13 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 3;

FIG. 14 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 3;

FIG. 15 is a cross-sectional view depicting an imaging lens according toEmbodiment 4;

FIG. 16 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 4;

FIG. 17 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 4;

FIG. 18 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 4;

FIG. 19 is a cross-sectional view depicting an imaging lens according toEmbodiment 5;

FIG. 20 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 5;

FIG. 21 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 5;

FIG. 22 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 5;

FIG. 23 is a cross-sectional view depicting an imaging lens according toEmbodiment 6;

FIG. 24 is a diagram depicting the distortion aberration of the imaginglens of Embodiment 6;

FIG. 25 is a diagram depicting the astigmatism aberration of the imaginglens of Embodiment 6; and

FIG. 26 is a diagram depicting the chromatic/spherical aberration of theimaging lens of Embodiment 6.

EXPLANATION OF REFERENCE NUMERALS

-   10: Image sensing element-   12: Cover glass-   14: First junction type compound lens-   16: Second junction type compound lens-   18: Third junction type compound lens-   50, 52, 54, 56, 58, 60: Adhesive-   70, 72, 74, 76, 78, 80: Coating film-   S: Stop (aperture stop)-   S₁: First stop-   S₂: Second stop-   L₁: First lens-   L₂: Second lens-   L₃: Third lens-   L₄: Fourth lens-   L₅: Fifth lens-   L₆: Sixth lens-   L₇: Seventh lens-   L₈: Eighth lens-   L₉: Ninth lens

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the drawings. Each drawing, however, simply illustrates oneconfiguration example of the present invention, and roughly shows across-section of each composing element and positional relationship inorder to assist in understanding the present invention, and is not forlimiting the present invention to the illustrated example in thefollowing description. Specific materials and conditions may be used,but these materials and conditions are merely examples of preferredembodiments, and therefore the present invention is not limited in anyway by these materials and conditions.

FIG. 1 is a diagram depicting a configuration of a first imaging lens ofthe present invention, and FIG. 6 is a diagram depicting a configurationof a second imaging lens of the present invention. Embodiments of thefirst imaging lens of the present invention are shown in Embodiment 1,Embodiment 4 and Embodiment 6. Embodiments of the second imaging lens ofthe present invention are shown in Embodiment 2, Embodiment 3 andEmbodiment 5.

As FIG. 1 and FIG. 6 shows, a first, second and third lensesconstituting a first junction type compound lens 14 are denoted with L₁,L₂ and L₃ respectively. A fourth, fifth and sixth lenses constituting asecond junction type compound lens 16 are denoted with L₄, L₅ and L₆respectively. And a seventh, eighth and ninth lenses constituting athird junction type compound lens 18 are denoted with L₇, L₈ and L₉respectively.

In the first imaging lens of the present invention shown in FIG. 1, astop S disposed between the first junction type compound lens 14 and thesecond junction type compound lens 16 plays a role of an aperture stop,and defines a position of an entrance pupil.

Whereas in the second imaging lens of the present invention shown inFIG. 6, a first stop S₁ disposed on the front face of the first junctiontype compound lens 14 (front face r₂ of the first lens) plays a role ofan aperture stop, and defines a position of an entrance pupil. A secondstop S₂ disposed between the first junction type compound lens 14 andthe second junction type compound lens 16 plays a role of preventing aflare, which is a phenomena of lowered image contrast, or a smear, whichis a phenomena of an image smearing.

In other words, in the second imaging lens of the present invention, thefirst stop S₁, which is a stop to play a role of determining the basiccharacteristics of the imaging lens, such as defining a position of anentrance pupil, specifying an F number and deciding various aberrationcharacteristics including distortion aberration and astigmatismaberration, is an essential composing element in the present invention.Whereas the second stop S₂ is a composing element for improving thecontrast of an image, that is, an added characteristic, thereforedisposing the second stop S₂ is preferable, but the imaging lens of thepresent invention is established without it.

Within a range where no misunderstanding occurs, r_(i) (i=1, 2, 3, . . ., 17) may be used as a variable that indicates a value of a radius ofcurvature on an optical axis, or as a symbol that identifies a lens,cover glass surface or image sensing plane (e.g. r₂ is used to indicatethe object side face of the first lens L₁ constituting the firstjunction type compound lens 14).

In FIG. 1, adhesives 50, 52, 54, 56, 58 and 60, for indirect bonding,exist on the interfaces indicated by r₂, r₃, r₇, r₈, r₁₁ and r₁₂respectively. If coating processing has been performed on both sides oron one side of the second lens L₂, the coating film 70 or coating film72 exists. If coating processing has been performed on both sides or onone side of the fifth lens L₅, the coating film 74 or coating film 76exists. If coating processing has been performed on both sides or on oneside of the eighth lens L₈, the coating film 78 or coating film 80exists. In order to indicate the presence of the adhesives 50, 52, 54,56, 58 and 60, and the coating films 70, 72, 74, 76, 78 and 80, theinterfaces indicated by r₂, r₃, r₇, r₈, r₁₁ and r₁₂ are shown by boldlines.

In FIG. 6, adhesives 50, 52, 54, 56, 58 and 60, for indirect bonding,exist on the interfaces indicated by r₃, r₄, r₈, r₉, r₁₂ and r₁₃respectively. If coating processing has been performed on both sides oron one side of the second lens L₂, the coating film 70 or coating film72 exists. If coating processing has been performed on both sides or onone side of the fifth lens L₅, the coating film 74 or coating film 76exists. If coating processing has been performed on both sides or on oneside of the eighth lens L₈, the coating film 78 or coating film 80exists. In order to indicate the presence of the adhesives 50, 52, 54,56, 58 and 60, and the coating films 70, 72, 74, 76, 78 and 80, theinterfaces indicated by r₃, r₄, r₈, r₉, r₁₂ and r₁₃ are shown by boldlines.

In FIG. 2, FIG. 7, FIG. 11, FIG. 15, FIG. 19 and FIG. 23, interfaceswhere the above mentioned adhesive or coating film exist are not shownby bold lines, and the adhesives 50, 52, 54, 56, 58 and 60, and coatingfilms 70, 72, 74, 76, 78 and 80 are omitted so that the drawings do notbecome complicated. In the imaging lens of the present invention, thethickness of the adhesive is small enough not to reflect the opticalcharacteristics of the imaging lens, so that the thickness of theadhesive is ignored, even if the adhesive exists on the interface.Needless to say, the bonding surfaces of the first and third lenses L₁and L₃, to be directly or indirectly bonded to the second lens L₂, havea shape matching the bonding surface of the second lens L₂, the bondingsurfaces of the fourth and sixth lenses L₄ and L₆, to be directly orindirectly bonded to the fifth lens L₅, have a shape matching thebonding surface of the fifth lens L₅, and the bonding surfaces of theseventh and ninth lenses L₇ and L₉, to be directly or indirectly bondedto the eight lens L₈, have a shape matching the bonding surface of theeight lens L₈.

Table 1 to Table 6 show the specific values of the parameters, such asr_(i) (i=1, 2, 3, . . . , 17), and d_(i) (i=1, 2, 3, . . . , 16)indicated in these drawings. The suffix i is added corresponding to thestops, surface number of each lens, thickness of the lens, or thesurface spacing of the lens sequentially from the object side to theimage side. j=1, 2, 3, . . . , 9 and indicate the first, second, third,. . . , ninth lens respectively. In other words, r_(i) is a radius ofcurvature on the optical axis on the i-th surface, d_(i) is a distancefrom then i-th surface to the (i+1)th surface, N₃ is a refractive indexof the j-th lens L₃, and ν_(j) is an Abbe number of the material of thej-th lens L.

The reference symbols of the surface number r_(i) (i=1, 2, 3, . . . ,17) and the surface spacing d_(i) (i=1, 2, 3, . . . , 16) defined inFIG. 1 and FIG. 6 are omitted in FIG. 2, FIG. 7, FIG. 11, FIG. 15, FIG.19 and FIG. 23 so that the drawings do not become complicated.

In FIG. 1 and FIG. 6, the aperture of the stop is shown by a segment.This is because the intersection of the stop surface and the opticalaxis must be clearly shown to define the distance from the lens surfaceto the stop surface. In FIG. 2, FIG. 7, FIG. 11, FIG. 15, FIG. 19 andFIG. 23, which are cross-sectional views of the imaging lenses ofEmbodiment 1 to Embodiment 6 respectively, a main body of the stop forshielding light is shown by the half lines of which start point is theedge of the aperture, by opening the aperture of the stop, which isunlike FIG. 1 and FIG. 6. This is because the state of the stop must beshown by opening the aperture of the stop in order to enter such a beamas a principal ray.

The optical length L is a distance from the object side face r₁ of thefirst lens L₁ to the image sensing plane in the first imaging lens, andis a distance from the first stop S₁ to the image sensing plane in thesecond imaging lens. The back focus bf is a distance from the image sidesurface of the ninth lens L₉ constituting the third junction typecompound lens 18 to the image sensing plane. Here the length from theimage side face of the ninth lens L₉ to the image sensing plane, whichis measured without a cover glass, is regarded as the back focus bf.

Table 1 to Table 6 show the thickness of the first to the third junctiontype compound lenses constituting the imaging lenses of Embodiment 1 toEmbodiment 6 respectively, and the data on the radius of curvature ofthe curved surfaces of the first to the ninth lenses constituting theselenses, and the positional spacing of these lenses and the positionalrelationship of these lenses and the stop. The aspherical data on thefirst, third, fourth, sixth, seventh and ninth lenses is shown in Table1 to Table 6 respectively with surface numbers. The value r_(i) (i=1, 2,3, . . . , 14) of the radius of curvature on the optical axis is apositive value if it is convex to the object side, and is a negativevalue if it is convex to the image side.

Both surfaces when the second lens is an optical-parallel plate, bothsurfaces when the fifth lens is an optical-parallel plate, both surfaceswhen the eighth lens is an optical-parallel plate, and surfaces of thestop S, the first stop S₁, the second stop S₂, and the cover glass (orfilter), are planes, so the radius of curvature is indicated as ∞. Theimage sensing plane is a plane, but r₁₆=∞ is omitted for r₁₆, whichindicates an image sensing plane in Table 1, Table 4 and Table 6. Alsor₁₇=∞ is omitted for r₁₇, which indicates an image sensing plane inTable 2, Table 3 and Table 5.

The aspherical surface used for this invention is given by the followingexpression.Z=ch ²/[1+[1−(1+k)c ² h ²]^(+1/2) ]+A ₄ h ⁴ +A ₆ h ⁶ +A ₈ h ⁸ +A ₁₀ h ¹⁰where

Z: depth from the vertex of the surface to the contact surface

c: curvature of the surface on the optical axis

h: height from the optical axis

k: cone constant

A₄: aspherical surface coefficient of degree 4

A₆: aspherical surface coefficient of degree 6

A₈: aspherical surface coefficient of degree 8

A₁₀: aspherical surface coefficient of degree 10

In Table 1 to Table 6 in this description, the numeric value to indicatean aspherical surface coefficient is denoted by an exponent, “e-1” forexample, which means “the −1th power of 10”. The value indicated as thefocal distance f is a composite focal distance of the first junctiontype compound lens, the second junction type compound lens, and thethird junction type compound lens. For each embodiment, the open Fnumber (also called an “open F value”), which is an index of thebrightness of the lens, is indicated by Fno. The open F number refers tothe F number when the diameter of the aperture stop is the maximum indesign specifications. The diagonal length 2Y of the square imagesurface is indicated as the image height. Y is a value half the diagonallength of the square image surface.

Now the imaging lenses according to Embodiment 1 to Embodiment 6 will bedescribed with reference to FIG. 1 to FIG. 26.

The distortion aberration curves shown in FIG. 3, FIG. 8, FIG. 12, FIG.16, FIG. 20 and FIG. 24 show the aberration (unsatisfactory quantity ofthe tangent condition is shown in the abscissa by percentage) withrespect to the distance from the optical axis (shown in the ordinate bypercentage with the maximum distance from the optical axis within theimage surface as 100). The astigmatism aberration curves shown in FIG.4, FIG. 9, FIG. 13, FIG. 17, FIG. 21 and FIG. 25 show the aberrationquantity (mm units) in the abscissa with respect to the distance fromthe optical axis (%) shown in the ordinate, just like the distortionaberration curves, and show the aberration quantity on the meridionalsurface and the sagittal surface respectively.

The chromatic/spherical aberration curve in FIG. 5, FIG. 10, FIG. 14,FIG. 18, FIG. 22 and FIG. 26 show the aberration quantity (mm units) inthe abscissa with respect to the entrance height h in the ordinate. Theentrance height h in the ordinate is shown as a value converted into anF number. For example, in the case of a lens of which Fno is 3.40, theentrance height h=100% of the ordinate corresponds to F=3.40.

For the chromatic/spherical aberration curves, the aberration valueswith respect to the C-line (light of which wavelength is 656.3 nm),d-line (light of which wavelength is 587.6 nm), e-line (light of whichwavelength is 546.1 nm), F-line (light of which wavelength is 486.1 nm)and g-line (light of which wavelength is 435.8 nm).

Table 1 to Table 6 show the list of the radius of curvature (mm units),lens surface spacing (mm units), refractive index of lens material, Abbenumber of lens material, focal distance, F number, image height andaspherical surface coefficient of composing lenses of Embodiment 1 toEmbodiment 6 respectively. The radius of curvature on the optical axisand the lens surface spacing of the composing lenses are shown as valueswhen the value of the composite focal distance f of the imaging lens isnormalized to 1.00 mm.

In Embodiment 1 to Embodiment 5, a transparent curable silicone resin,which is a curable resin material, is used for the material of the firstlens L₁ and the third lens L₃ constituting the first junction typecompound lens 14, material of the fourth lens L₄ and the sixth lens L₆constituting the second junction type compound lens 16, and material ofthe seventh lens L₇ and the ninth lens L₉ constituting the thirdjunction type compound lens 18. Optical glass (e.g. BK7), which is anoptical glass material, is used for the material of the second lens L₂,fifth lens L₅ and eighth lens L₈. Here BK7 is a name assigned by SchottGlass Co. to a group of boro-silicate glass. Optical glass BK7 is nowmanufactured by a plurality of glass manufacturers.

In Embodiment 6, a thermosetting silicone resin Silplus MHD, which is acurable resin material made by Nippon Steel Chemical Co., Ltd., is usedfor the materials of the second lens L₂, fifth lens L₅ and eighth lensL₈.

The refractive index and the Abbe number of commercial optical glass BK7differ somewhat depending on the manufacturer or manufacturing lot. Therefractive index of the optical glass BK7 (made by Ohara Inc.) withrespect to the d-line (light with 587.6 nm wavelength) constituting thesecond lens L₂, fifth lens L₅ and eighth lens L₈ is 1.51633, and theAbbe number thereof is 64.0. The refractive index of the optical glassE-F5 (made by Hoya Corp.) with respect to the d-line (light with 587.6nm wavelength) constituting the fifth lens L₅ of Embodiment 3 is1.60342, and the Abbe number thereof is 38.0.

The transparent curable silicone resin refers to a silicone resin whichis transparent to visible lights and with which the geometric shape of alens does not change, and the optical performance does not deteriorateeven if the environment temporarily becomes about 150° C. hightemperature. The transparent curable silicone resin mentioned here canbe selected from silicone resins commercialized under the name“transparent high hardness silicone resin” by silicone resin suppliers,for example.

In Embodiment 1 to Embodiment 5, the first lens L₁ and the second lensL₂ are indirectly bonded, and the second lens L₂ and the third lens L₃are indirectly bonded. The fourth lens L₄ and the fifth lens L₅ areindirectly bonded, and the fifth lens L₅ and the sixth lens L₆ areindirectly bonded. The seventh lens L₇ and the eighth lens L₈ areindirectly bonded, and the eighth lens L₈ and the ninth lens L₉ areindirectly bonded. In Embodiment 6, the first lens L₁ and the secondlens L₂ are directly bonded or indirectly bonded, and the second lens L₂and the third lens L₃ are directly bonded or indirectly bonded. Thefourth lens L₄ and the fifth lens L₅ are directly bonded or indirectlybonded, and the fifth lens L₅ and the sixth lens L₆ are directly bondedor indirectly bonded. The seventh lens L₇ and the eighth lens L₈ aredirectly bonded or indirectly bonded, and the eighth lens L₈ and theninth lens L₉ are directly bonded or indirectly bonded.

For the curable resin material, which is a material of the first lensL₁, the third lens L₃, the fourth lens L₄, the sixth lens L₆, theseventh lens L₇ and the ninth lens L₉, SMX-7852 and SMX-7877 made byFuji Polymer Industries Co., Ltd., and SR-7010 made by Dow Corning TorayCo., Ltd. are used. The refractive indexes and the Abbe numbers of thesethermosetting silicone resins differ depending on the manufacturer andalso differ somewhat even if the product name is the same. In thefollowing embodiments, the thermosetting silicone resin material whichwas used is shown, along with the refractive index (d-line (light with587.6 nm wavelength)) and the Abbe number thereof.

Epoxy adhesive can be used for an adhesive for the above mentionedindirect bonding. Specifically, a refractive index matching type opticaladhesive (e.g. see <URL: http://keytech.ntt-at.co.jp/optic2/prd1001.html> of NTT Advanced Technology Co. [searched on May 7, 2007]) canbe used. This refractive index matching type optical adhesive hasdurability under heat, and even if this lens is temporarily placed in ahigh temperature environment, a form change, such as melting, does notoccur, and the optical performance does not deteriorate. This refractiveindex matching type optical adhesive is transparent to visible lights,and the refractive index thereof can be adjusted in the range of 1.33 to1.70 at a ±0.005 accuracy. As mentioned later, for the first to theninth lenses constituting the junction type compound lens used for theimaging lens of the present invention, a material of which refractiveindex is in a 1.33 to 1.70 range is used. Therefore this refractiveindex matching type optical adhesive can be manufactured withcontrolling the refractive index thereof to be a value close to all therefractive indexes of the first to the ninth lenses.

The adhesive to be used for indirect bonding is not limited to the abovementioned example of the refractive index matching type opticaladhesive, but can be any adhesive which is transparent and whichsatisfies the conditions of the refractive index and heat resistance. Acondition for the refractive index of the adhesive is that therefractive index of the adhesive is close to both of the refractiveindexes of the two lenses to be bonded. A condition for the heatresistance is that even if the adhesive, which is solidified and is in astate of bonding the two lenses, is placed in a high temperatureenvironment in the reflow step or is placed in an environment whichtemporarily becomes high temperature, a form change, such as melting,does not occur, and optical performance thereof does not change.

As FIG. 1 shows, the first imaging lens of the present inventioncomprises a first junction type compound lens 14, a stop S (aperturestop), a second junction type compound lens 16, and a third junctiontype compound lens 18, where the first junction type compound lens 14,the stop S, the second junction type compound lens 16 and the thirdjunction type compound lens 18 are arranged in this sequence from theobject side to the image side.

As FIG. 6 shows, the second imaging lens of the present inventioncomprises a first stop S₁, a first junction type compound lens 14, asecond stop S₂, a second junction type compound lens 16, and a thirdjunction type compound lens 18, where the first stop S₁, the firstjunction type compound lens 14, the second stop S₂, the second junctiontype compound lens 16, and the third junction type compound lens 18 arearranged in this sequence froth the object side to the image side.

The first junction type compound lens 14 comprises a first lens L₁, asecond lens L₂ and a third lens L₂, which are arranged in this sequencefrom the object side to the image side. The second junction typecompound lens 16 comprises a fourth lens L₄, a fifth lens L₅ and a sixthlens L₆, which are arranged in this sequence from the object side to theimage side. The third junction type compound lens 18 comprises a seventhlens L₇, an eighth lens L₈ and a ninth lens L₉, which are arranged inthis sequence from the object side to the image side.

A color glass 12 is inserted between the third junction type compoundlens 18 and the image sensing element 10. A material of the cover glass12 is optical glass BK7 (made by Hoya Corp.) of which refractive indexis 1.51633 and the Abbe number is 64.0. In the later mentioned Table 1to Table 6, the refractive index and the Abbe number of the cover glass12 are shown as N=1.51633 and ν=64.0 respectively.

Table 1 to Table 6 show the value r_(i) (i=1, 2, 3, . . . , 16) of theradius of curvature on the optical axis, surface spacing d_(i) (i=1, 2,3, . . . , 16) and refractive index, Abbe number and aspherical surfacecoefficient of the lens composing material of the imaging lenses ofEmbodiment 1 to Embodiment 6. Here the composite focal distance by thefirst junction type compound lens, the second junction type compoundlens and the third junction type compound lens is normalized to 1.00 mm.

The object side face of the first lens L₁ and the image side face of thethird lens L₃ constituting the first junction type compound lens 14 areaspherical, the object side face of the fourth lens L₄ and the imageside face of the sixth lens L₆ constituting the second junction typecompound lens 16 are aspherical, and the object side face of the seventhlens L₇ and the image side face of the ninth lens L₉ constituting thethird junction type compound lens 18 are aspherical.

TABLE 1 Embodiment 1 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = 0.290 2.679e−1 −3.062e−1 3.708 −9.974e+1 3.512e+3 d₁= 0.1553 N₁ = 1.51000 ν₁ = 56.0 r₂ = ∞ d₂ = 0.0945 N₂ = 1.51633 ν₂ =64.0 r₃ = ∞ d₃ = 0.0105 N₃ = 1.51000 ν₃ = 56.0 r₄ = 0.661 1.087e+1 3.263−6.012e+1 −1.969e+3 2.877e+5 d₄ = 0.0144 r₅ = ∞ d₅ = 0.0589 r₆ = −0.3074.656e−1 5.992 −1.188e+3 1.130e+5 −4.010e+6 d₆ = 0.0057 N₄ = 1.51000 ν₄= 56.0 r₇ = ∞ d₇ = 0.1574 N₅ = 1.51633 ν₅ = 64.0 r₈ = ∞ d₈ = 0.0735 N₆ =1.51000 ν₆ = 56.0 r₉ = −0.372 −2.627e−1 9.387 −1.849 −1.329e+1 −2.264e+3d₉ = 0.0355 r₁₀ = 2.495 3.033e+1 8.360e−1 1.675 −7.945 −3.142e+1 d₁₀ =0.0738 N₇ = 1.51000 ν₇ = 56.0 r₁₁ = ∞ d₁₁ = 0.0839 N₈ = 1.51633 ν₈ =64.0 r₁₂ = ∞ d₁₂ = 0.0315 N₉ = 1.51000 ν₉ = 56.0 r₁₃ = 1.839 −2.401e+1−5.705 3.180e+1 −9.030e+1 1.766e+2 d₁₃ = 0.2295 r₁₄ = ∞ d₁₄ = 0.1049 N =1.51633 ν = 64.0 r₁₅ = ∞ d₁₅ = 0.1000 Focal Distance f = 1.00 mmF-Number F_(no) = 3.40 Image Height 2Y = 1.172 mm

TABLE 2 Embodiment 2 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = ∞ d₁ = 0.0000 r₂ = 0.324 1.102 −5.858 −1.033e+23.814e+3 −2.282e+5 d₂ = 0.0694 N₁ = 1.51000 ν₁ = 56.0 r₃ = ∞ d₃ = 0.0785N₂ = 1.51633 ν₂ = 64.0 r₄ = ∞ d₄ = 0.0262 N₃ = 1.51000 ν₃ = 56.0 r₅ =−51.004 1.791e+4 −8.623 −1.712e+1 −4.432e+3 −1.243e+5 d₅ = 0.0219 r₆ = ∞d₆ = 0.0890 r₇ = −0.216 1.473e−1 1.714e+1 2.890e+2 1.357e+3 −3.232e+5 d₇= 0.0157 N₄ = 1.51000 ν₄ = 56.0 r₈ = ∞ d₈ = 0.0654 N₅ = 1.51633 ν₅ =64.0 r₉ = ∞ d₉ = 0.0393 N₆ = 1.51000 ν₆ = 56.0 r₁₀ = −0.318 −1.587 5.2675.294e+2 −5.318e+3 1.001e+4 d₁₀ = 0.0953 r₁₁ = 0.917 −2.434e+2 −4.2873.777e+1 −1.443e+2 2.430e+2 d₁₁ = 0.0091 N₇ = 1.51000 ν₇ = 56.0 r₁₂ = ∞d₁₂ = 0.1047 N₈ = 1.51633 ν₈ = 64.0 r₁₃ = ∞ d₁₃ = 0.0837 N₉ = 1.51000 ν₉= 56.0 r₁₄ = 0.465 −2.873e+1 −3.141 9.020e−2 2.310e+1 −1.201e+2 d₁₄ =0.2022 r₁₅ = ∞ d₁₅ = 0.0785 N = 1.51633 ν = 64.0 r₁₆ = ∞ d₁₆ = 0.1000Focal Distance f = 1.00 mm F-Number F_(no) = 2.90 Image Height 2Y =1.260 mm

TABLE 3 Embodiment 3 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = ∞ d₁ = 0.0000 r₂ = 0.351 1.340 −5.036 −1.009e+22.086e+3 −1.402e+5 d₂ = 0.0597 N₁ = 1.53000 ν₁ = 35.0 r₃ = ∞ d₃ = 0.0878N₂ = 1.51633 ν₂ = 64.0 r₄ = ∞ d₄ = 0.0329 N₃ = 1.53000 ν₃ = 35.0 r₅ =−17.554 1.062e+4 −7.948 −6.007e+1 −2.578e+3 −6.919e+4 d₅ = 0.0211 r₆ = ∞d₆ = 0.0940 r₇ = −0.214 2.700e−2 1.110e+1 3.585e+2 2.293e+2 −1.379e+5 d₇= 0.0147 N₄ = 1.60000 ν₄ = 30.0 r₈ = ∞ d₈ = 0.0658 N₅ = 1.60342 ν₅ =38.0 r₉ = ∞ d₉ = 0.0439 N₆ = 1.60000 ν₆ = 30.0 r₁₀ = −0.343 −5.390e−15.032e−1 4.563e+2 −3.511e+3 8.214e+3 d₁₀ = 0.0987 r₁₁ = 0.614 −4.296e+1−3.386 2.668e+1 −1.135e+2 2.311e+2 d₁₁ = 0.0292 N₇ = 1.53000 ν₇ = 35.0r₁₂ = ∞ d₁₂ = 0.1097 N₈ = 1.51633 ν₈ = 64.0 r₁₃ = ∞ d₁₃ = 0.0658 N₉ =1.53000 ν₉ = 35.0 r₁₄ = 0.530 −2.100e+1 −3.682 1.083e+1 −3.730e+13.258e+1 d₁₄ = 0.2477 r₁₅ = ∞ d₁₅ = 0.0658 N = 1.51633 ν = 64.0 r₁₆ = ∞d₁₆ = 0.1000 Focal Distance f = 1.00 mm F-Number F_(no) = 2.96 ImageHeight 2Y = 1.262 mm

TABLE 4 Embodiment 4 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = 0.295 2.680e−1 −2.911e−1 3.410 −8.867e+1 3.019e+3 d₁= 0.0596 N₁ = 1.51000 ν₁ = 56.0 r₂ = 0.344 d₂ = 0.1945 N₂ = 1.51633 ν₂ =64.0 r₃ = 1.475 d₃ = 0.0108 N₃ = 1.51000 ν₃ = 56.0 r₄ = 0.672 1.088e+13.103 −5.527e+1 −1.750e+3 2.473e+5 d₄ = 0.0147 r₅ = ∞ d₅ = 0.0599 r₆ =−0.312 4.656e−1 5.697 −1.092e+3 1.005e+5 −3.447e+6 d₆ = 0.0058 N₄ =1.51000 ν₄ = 56.0 r₇ = −0.984 d₇ = 0.1994 N₅ = 1.51633 ν₅ = 64.0 r₈ =−0.787 d₈ = 0.0354 N₆ = 1.51000 ν₆ = 56.0 r₉ = −0.378 −2.630e−1 8.926−1.700 −1.181e+1 −1.946e+3 d₉ = 0.0361 r₁₀ = 2.538 3.033e+1 7.948e−11.540 −7.063 −2.701e+1 d₁₀ = 0.0357 N₇ = 1.51000 ν₇ = 56.0 r₁₁ = 2.360d₁₁ = 0.1444 N₈ = 1.51633 ν₈ = 64.0 r₁₂ = −2.262 d₁₂ = 0.0124 N₉ =1.51000 ν₉ = 56.0 r₁₃ = 1.871 −2.401e+1 −5.424 2.924e+1 −8.027e+11.518e+2 d₁₃ = 0.2200 r₁₄ = ∞ d₁₄ = 0.1067 N = 1.51633 ν = 64.0 r₁₅ = ∞d₁₅ = 0.1001 Focal Distance f = 1.00 mm F-Number F_(no) = 3.40 ImageHeight 2Y = 1.144 mm

TABLE 5 Embodiment 5 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = ∞ d₁ = 0.0000 r₂ = 0.325 1.102 −5.758 −1.004e+23.664e+3 −2.166e+5 d₂ = 0.0509 N₁ = 1.51000 ν₁ = 56.0 r₃ = 1.421 d₃ =0.1074 N₂ = 1.51633 ν₂ = 64.0 r₄ = −0.947 d₄ = 0.0168 N₃ = 1.51000 ν₃ =56.0 r₅ = −51.298 1.791e+4 −8.476 −1.663e+1 −4.257e+3 −1.180e+5 d₅ =0.0221 r₆ = ∞ d₆ = 0.0895 r₇ = −0.218 1.473e−1 1.684e+1 2.808e+21.304e+3 −3.068e+5 d₇ = 0.0158 N₄ = 1.51000 ν₄ = 56.0 r₈ = −0.379 d₈ =0.0848 N₅ = 1.51633 ν₅ = 64.0 r₉ = −0.947 d₉ = 0.0206 N₆ = 1.51000 ν₆ =56.0 r₁₀ = −0.320 −1.587 5.177 5.144e+2 −5.108e+3 9.503e+3 d₁₀ = 0.0958r₁₁ = 0.923 −2.434e+2 −4.214 3.670e+1 −1.386e+2 2.307e+2 d₁₁ = 0.0284 N₇= 1.51000 ν₇ = 56.0 r₁₂ = −4.735 d₁₂ = 0.1524 N₈ = 1.51633 ν₈ = 64.0 r₁₃= −1.894 d₁₃ = 0.0179 N₉ = 1.51000 ν₉ = 56.0 r₁₄ = 0.467 −2.873e+1−3.087 8.764e−2 2.219e+1 −1.141e+2 d₁₄ = 0.1980 r₁₅ = ∞ d₁₅ = 0.0788 N =1.51633 ν = 64.0 r₁₆ = ∞ d₁₆ = 0.1000 Focal Distance f = 1.00 mmF-Number F_(no) = 2.80 Image Height 2Y = 1.240 mm

TABLE 6 Embodiment 6 Radius of Refractive Abbe Aspherical SurfaceCoefficients Curvature(r_(i)) Distance(d_(i)) Index(N_(i)) Number(ν_(i))K A₄ A₆ A₈ A₁₀ r₁ = 0.2897 2.679e−1 −3.062e−1 3.708 −9.974e+1 3.512e+3d₁ = 0.1553 N₁ = 1.51000 ν₁ = 56.0 r₂ = ∞ d₂ = 0.0945 N₂ = 1.51100 ν₂ =36.0 r₃ = ∞ d₃ = 0.0105 N₃ = 1.51000 ν₃ = 56.0 r₄ = 0.6609 1.087e+13.263 −6.012e+1 −1.969e+3 2.877e+5 d₄ = 0.0144 r₅ = ∞ d₅ = 0.0589 r₆ =−0.3072 4.656e−1 5.992 −1.188e+3 1.130e+5 −4.010e+6 d₆ = 0.0057 N₄ =1.51000 ν₄ = 56.0 r₇ = ∞ d₇ = 0.1574 N₅ = 1.51100 ν₅ = 36.0 r₈ = ∞ d₈ =0.0735 N₆ = 1.51000 ν₆ = 56.0 r₉ = −0.3720 −2.627e−1 9.387 −1.849−1.329e+1 −2.264e+3 d₉ = 0.0355 r₁₀ = 2.4953 3.033e+1 8.360e−1 1.675−7.945 −3.142e+1 d₁₀ = 0.0738 N₇ = 1.51000 ν₇ = 56.0 r₁₁ = ∞ d₁₁ =0.0839 N₈ = 1.51100 ν₈ = 36.0 r₁₂ = ∞ d₁₂ = 0.0315 N₉ = 1.51000 ν₉ =56.0 r₁₃ = 1.8395 −2.401e+1 −5.705 3.180e+1 −9.030e+1 1.766e+2 d₁₃ =0.2295 r₁₄ = ∞ d₁₄ = 0.1049 N = 1.51633 ν = 64.0 r₁₅ = ∞ d₁₅ = 0.0991Focal Distance f = 1.00 mm F-Number F_(no) = 3.40 Image Height 2Y =1.172 mm

The junction type compound lenses used in Embodiment 1 to Embodiment 5are manufactured by indirectly bonding lenses. This indirect bonding isimplemented by using an adhesive there between. Since this procedure isthe same for both the first junction type compound lens, the secondjunction type compound lens, and the third junction type compound lens,the first junction type compound lens will be described here as anexample. In this case, the first to the third lens, L₁ to L₃, are formedfirst, then adhesive is coated on the surface of the second lens L₂facing the first lens L₁ or the third lens L₃, or on the surface of thefirst lens L₁ or the third lens L₃, facing the second lens L₂, and bothlenses are contacted.

Coating processing could be performed at least on one surface of thesecond lens L₂ facing the first lens L₁ or the third lens L₃, then bothlenses are bonded. In this case, indirect bonding or direct bonding,mentioned below, could be performed after the coating processing.

The junction type compound lens used for Embodiment 6 is manufactured bydirectly bonding or indirectly bonding the lenses.

The following steps are performed (for details, see Patent No. 3926380)to manufacture the junction type compound lens by direct bonding. Inthis case as well, the procedure is the same for the first junction typecompound lens, the second junction type compound lens, and the thirdtype compound lens, so the first junction type compound lens will bedescribed here as an example.

A die for forming the first lens L₁, that can be bonded to the secondlens L₂, is prepared. This die is a cylinder where the side wall of theinner face is cylindrical, and the bottom face is a curved shape, thesame as the object side face of the first lens L₁. A transparent curablesilicone resin, which is in a liquid state before curing, is injectedinto the die, and thermo-curing processing or UV curing processing isperformed to form the first lens L₁, and the first lens L₁ is bonded tothe second lens L₂.

Then a die for forming the third lens L₃, which is bonded to the abovecompound lens where the first lens L₁ and the second lens L₂ are bonded,is prepared. The bottom face of this die has a shape the same as theimage face of the third lens L₃. A transparent curable silicone resin,which is in a liquid state before curing, is injected into the die,thermo-curing processing or UV curing processing is performed to formthe third lens L₃, and the third lens L₃ is bonded to the second lensL₂, where the first lens L₁ is bonded. Thus the junction type compoundlens is formed.

In the above mentioned manufacturing steps of the junction type compoundlens, if the first lens L₁ and the third lens L₃ are formed ofthermosetting resin material, a temperature control device forincreasing the temperature of the dies and controlling processing isrequired. If the first lens L₁ and the third lens L₃ are formed of a UVcurable resin, the manufacturing device for the junction type compoundlens is designed so that ultraviolet can be irradiated onto the UVcurable resin from an area above the die.

Embodiment 1

Embodiment 1 is an embodiment of the first imaging lens of the presentinvention, where the first lens L₁, the third lens L₃, the fourth lensL₄, the sixth lens L₆, the seventh lens L₇ and the ninth lens L₉ areformed of transparent curable silicone resin SMX-7852 (made by FujiPolymer Industries Co. Ltd.), and the second lens L₂, the fifth lens L₅and the eighth lens L₈ are formed of optical glass BK7 (made by OharaInc.).

-   (A) The refractive index N₁ of the first lens L₁ is N₁=1.51000.-   (B) The refractive index N₂ of the second lens L₂ is N₂=1.51633.-   (C) The refractive index N₃ of the third lens L₃ is N₃=1.51000.-   (D) The Abbe number ν₁ of the first lens L₁ is ν₁=56.0.-   (E) The Abbe number ν₂ of the second lens L₂ is ν₂=64.0.-   (F) The Abbe number ν₃ of the third lens L₃ is ν₃=56.0.-   (G) The refractive index N₄ of the fourth lens L₄ is N₄=1.51000.-   (H) The refractive index N₅ of the fifth lens L₅ is N₅=1.51633.-   (I) The refractive index N₆ of the sixth lens L₆ is N₆=1.51000.-   (J) The Abbe number ν₄ of the fourth lens L₄ is ν₄=56.0.-   (K) The Abbe number ν₅ of the fifth lens L₅ is ν₅=64.0.-   (L) The Abbe number ν₆ of the sixth lens L₆ is ν₆=56.0.-   (M) The refractive index N₇ of the seventh lens L₇ is N₇=1.51000.-   (N) The refractive index N₈ of the eighth lens L₈ is N₈=1.51633.-   (O) The refractive index Ng of the ninth lens L₉ is N₉=1.51000.-   (P) The Abbe number ν₇ of the seventh lens L₇ is ν₇=56.0.-   (Q) The Abbe number ν₈ of the eighth lens L₈ is ν₈=64.0.-   (R) The Abbe number ν₉ of the ninth lens L₉ is ν₉=56.0.

Therefore |N₂−N₁|=|N₂−N₃|=|N₅−N₄|=|N₅−N₆|=|N₈−N₇|=|N₈−N₉|=0.00633, whichsatisfies the following Conditions (1), (2), (5), (6), (9) and (10).Also |ν₂−ν₁|=|ν₂−ν₃|=|ν₅−ν₄|=|ν₅−ν₆|=|ν₈−ν₇|=|ν₈−ν₉|=8.0, whichsatisfies the following Conditions (3), (4), (7), (8), (11) and (12).

The Conditions (1), (2), (5), (6), (9) and (10) refer to the Conditionsgiven by Expression (1), (2), (5), (6), (9) and (10) respectively. TheConditions (3), (4), (7), (8), (11) and (12) refer to the Conditionsgiven by Expression (3), (4), (7), (8), (11) and (12).0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦ν₂−ν₁|≦30.0  (3)0≦ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12)

The Conditions (1) to (12) refer to the Conditions given by Expression(1) to (12) respectively, which is the same for the description hereinbelow (description on Embodiment 2 to Embodiment 5).

FIG. 2 is a cross-sectional view of the imaging lens of Embodiment 1. AsFIG. 2 shows, the aperture stop S is formed between the first junctiontype compound lens 14 and the second junction type compound lens 16. Thestop surface of the aperture stop S is a plane, so r₅=∞ is indicated inTable 1. The F number Fno is 3.40.

As Table 1 shows, r₂=∞ and r₃=∞, so the second lens L₂ is anoptical-parallel plate, r₇=∞ and r₈=∞, so the fifth lens L₅ is anoptical-parallel plate, and r₁₁=∞ and r₁₂=∞, so the eighth lens L₈ is anoptical-parallel plate.

r₁ is a positive value and r₄ is a positive value, so the first lens L₁is a plano-convex lens where the object side face of this first lens L₁is a convex surface facing the object side on a paraxial line, and thethird lens L₃ is a plano-concave lens where the image side face of thisthird lens L₃ is a concave surface facing the image side on a paraxialline. r₆ is a negative value and r₉ is also a negative value, so thefourth lens L₄ is a plano-concave lens where the object side face ofthis fourth lens L₄ is a concave surface facing the object side on aparaxial line, and the sixth lens L₆ is a plano-convex lens where theimage side face of this sixth lens L₆ is a convex surface facing theimage side on a paraxial line. r₁₀ is a positive value and r₁₃ is also apositive value, so the seventh lens L₇ is a plano-convex lens where theobject side face of this seventh lens L₇ is a convex surface facing theobject side on a paraxial line, and the ninth lens L₉ is a plano-concavelens where the image side face of this ninth lens L₉ is a concavesurface facing the image side on a paraxial line.

In Embodiment 1, the optical length L with respect to the focal distancef=1.00 mm is 1.229 mm, and the back focus bf is 0.399 mm.

FIG. 3 shows a graph of the distortion aberration curve 1-1, FIG. 4shows a graph of the astigmatism aberration curve (aberration curve 1-2on the meridional surface and aberration curve 1-3 on the sagittalsurface), and FIG. 5 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 1-4 on g-line, aberration curve 1-5 on F-line,aberration curve 1-6 on e-line, aberration curve 1-7 on d-line, andaberration curve 1-8 on C-line).

The ordinates of the aberration curves in FIG. 3 and FIG. 4 show theimage height by a % of the distance from the optical axis. In FIG. 3 andFIG. 4, 100% corresponds to 0.586 mm. The ordinate of the aberrationcurve in FIG. 5 shows the entrance height h (F number), and the maximumthereof corresponds to 3.40. The abscissa of FIG. 3 shows the aberration(%), and the abscissas of FIG. 4 and FIG. 5 show the value of theaberration (mm).

For the distortion aberration, the absolute value of the aberration is5.41%, which is the maximum, at the position of 100% image height (imageheight: 0.586 mm), and the absolute value of the aberration is within5.41% in a range where the image height is 0.586 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe meridional surface is 0.0675 mm, which is the maximum, at theposition of 100% image height (image height: 0.586 mm), and the absolutevalue of the aberration is within 0.0675 mm in a range where the imageheight is 0.586 mm or less.

For the chromatic/spherical aberration, the absolute value of theaberration curve 1-4 on the g-line is 0.0234 mm, which is the maximum,at 100% entrance height h, and the absolute value of the aberration iswithin 0.0234 mm.

Therefore according to the imaging lens of Embodiment 1, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcover glass between the imaging lens and the image sensing plane, andgood images can be acquired.

Embodiment 2

Embodiment 2 is an embodiment of the second imaging lens of the presentinvention, where the first lens L₁, the third lens L₃, the fourth lensL₄, the sixth lens L₆, the seventh lens L₇ and the ninth lens L₉ areformed of a transparent curable silicone resin SMX-7852 (made by FujiPolymer Industries Co. Ltd.), and the second lens L₂, the fifth lens L₅and the eighth lens L₈ are formed of optical glass BK7 (made by OharaInc.)

The respective composing materials of the first to the ninth lens arethe same as the above mentioned Embodiment 1, therefore|N₂−N₁|=|N₂−N₃|=|N₅−N₄|=|N₅−N₆|=|N₈−N₇|=|N₈−N₉|=0.00633, which satisfiesthe following Conditions (1), (2), (5), (6), (9) and (10). Also|ν₂−ν₁|=|ν₂−ν₃|=|ν₅−ν₄|=|ν₅−ν₆|=|ν₈−ν₇|=|ν₈−ν₉|=8.0, which satisfies thefollowing Conditions (3), (4), (7), (8), (11) and (12).

FIG. 7 is a cross-sectional view of the imaging lens of Embodiment 2. AsFIG. 7 shows, the first stop S₁, to play a role of an aperture stop, isformed at a position of an intersection of the first surface (surface atthe object side) of the first lens L₁ constituting the first junctiontype compound lens 14 and the optical axis. The second stop S₂, to playa role of preventing a flare or smear, is formed between the firstjunction type compound lens 14 and the second junction type compoundlens 16.

The stop surface of the first stop S₁ is a plane r₁, so r₁=∞ isindicated in Table 2. The second stop S₂ is comprised of a plane r₆, sor₆=∞ is indicated in Table 2. The F number Fno is 2.90.

As Table 2 shows, r₃=∞ and r₄=∞, so the second lens L₂ is anoptical-parallel plate, r₈=∞ and r₉=∞, so the fifth lens L₅ is anoptical-parallel plate, and r₁₂=∞ and r₁₃=∞, so the eighth lens L₈ is anoptical-parallel plate.

Further, r₂ is a positive value and r₅ is a negative value, so the firstlens L₁ is a plano-convex lens where the object side face of this firstlens L₁ is a convex surface facing the object side on a paraxial line,and the third lens L₃ is a plano-convex lens where the image side faceof this third lens L₃ is a convex surface facing the image side on aparaxial line. r₇ is a negative value and r₁₀ is also a negative value,so the fourth lens L₄ is a plano-concave lens where the object side faceof this fourth lens L₄ is a concave surface facing the object side on aparaxial line, and the sixth lens L₆ is a plano-convex lens where theimage side face of this sixth lens L₆ is a convex surface facing theimage side on a paraxial line. r₁₁ is a positive value and r₁₄ is also apositive value, so the seventh lens L₇ is a plano-convex lens where theobject side face of this seventh lens L₇ is a convex surface facing theobject side, and the ninth lens L₉ is a plano-concave lens where theimage side face of this ninth lens L₉ is a concave surface facing theimage side on a paraxial line.

In Embodiment 2, the optical length L with respect to the focal distancef=1.00 mm is 1.079 mm, and the back focus bf is 0.352 mm.

FIG. 8 shows a graph of the distortion aberration curve 2-1, FIG. 9shows a graph of the astigmatism aberration curve (aberration curve 2-2on the meridional surface and aberration curve 2-3 on the sagittalsurface), and FIG. 10 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 2-4 on g-line, aberration curve 2-5 on F-line,aberration curve 2-6 on e-line, aberration curve 2-7 on d-line, andaberration curve 2-8 on C-line).

The ordinates of the aberration curves in FIG. 8 and FIG. 9 show theimage height by a % of the distance from the optical axis. In FIG. 8 andFIG. 9, 100% corresponds to 0.630 mm. The ordinate of the aberrationcurve in FIG. 10 shows the entrance height h (F number), and the maximumthereof corresponds to 2.90. The abscissa of FIG. 8 shows the aberration(%), and the abscissa of FIG. 9 and FIG. 10 show the value of theaberration (mm).

For the distortion aberration, the absolute value of the aberration is1.68%, which is the maximum, at the position of 100% image height (imageheight: 0.630 mm), and the absolute value of the aberration is within1.68% in a range where the image height is 0.630 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe meridional surface is 0.0292 mm, which is the maximum, at theposition of 100% image height (image height: 0.630 mm), and the absolutevalue of the aberration is within 0.0292 mm in a range where the imageheight is 0.630 mm or less.

For the chromatic/spherical aberration, the absolute value of theaberration curve 2-4 on the g-line is 0.0534 mm, which is the maximum,at 100% entrance height h, and the absolute value of the aberration iswithin 0.0534 mm.

Therefore according to the imaging lens of Embodiment 2, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcover glass between the imaging lens and the image sensing plane, andgood images can be. acquired.

Embodiment 3

Embodiment 3 is an embodiment of the second imaging lens of the presentinvention, wherein the first lens L₁, the third lens L₃, the seventhlens L₇, and the ninth lens L₉ are formed of transparent curablesilicone resin SR-7010 (made by Dow Corning Toray Co., Ltd.), the secondlens L₂ and the eighth lens L₈ are formed of optical glass BK7 (made byOhara Inc.), and the fifth lens L₅ is formed of optical glass E-F5 (madeby Hoya Corp). And the fourth lens L₄ and the sixth lens L₆ are formedof transparent curable silicone resin SMX-7877 (made by Fuji PolymerIndustries Co. Ltd)).

-   (A) The refractive index N₁ of the first lens L₁ is N₁=1.53000.-   (B) The refractive index N₂ of the second lens L₂ is N₂=1.51633.-   (C) The refractive index N₃ of the third lens L₃ is N₃=1.53000.-   (D) The Abbe number ν₁ of the first lens L₁ is ν₁=35.0.-   (E) The Abbe number ν₂ of the second lens L₂ is ν₂=64.0.-   (F) The Abbe number ν₃ of the third lens L₃ is ν₃=35.0.-   (G) The refractive index N₄ of the fourth lens L₄ is N₄=1.60000.-   (H) The refractive index N₅ of the fifth lens L₅ is N₅=1.60342.-   (I) The refractive index N₆ of the sixth lens L₆ is N₆=1.60000.-   (J) The Abbe number ν₄ of the fourth lens L₄ is ν₄=30.0.-   (K) The Abbe number ν₅ of the fifth lens L₅ is ν₅=38.0.-   (L) The Abbe number ν₆ of the sixth lens L₆ is ν₆=30.0.-   (M) The refractive index N₇ of the seventh lens L₇ is N₇=1.53000.-   (N) The refractive index N₈ of the eighth lens L₈ is N₈=1.51633.-   (O) The refractive index N₉ of the ninth lens L₉ is N₉=1.53000.-   (P) The Abbe number ν₇ of the seventh lens L₇ is ν₇=35.0.-   (Q) The Abbe number ν₈ of the eighth lens L₈ is ν₈=64.0.-   (R) The Abbe number ν₉ of the ninth lens L₉ is ν₉=35.0

Therefore |N₂−N₁|=|N₂−N₃|=|N₈−N₇|=|N₈−N₉|=0.01367, and|N₅−N₄|=|N₅−N₆|=0.00342, which satisfies the following Conditions (1),(2), (5), (6), (9) and (10). Also |ν₂−ν₁|=|ν₂−ν₃|=|ν₈−ν₇|=|ν₈−ν₉|=29.0and |ν₅−ν₄|=|ν₅−ν₆|=8.0, which satisfies the following Conditions (3),(4), (7), (8), (11) and (12).

FIG. 11 is a cross-sectional view of the imaging lens of Embodiment 3.As FIG. 11 shows, the first stop S₁, to play a role of an aperture stop,is formed at a position of an intersection of the first surface (surfaceat the object side) of the first lens L₁ constituting the first junctiontype compound lens 14 and the optical axis. The second stop S₂, to playa role of preventing a flare or smear, is formed between the firstjunction type compound lens 14 and the second junction type compoundlens 16.

The stop surface of the first stop S₁ is a plane r_(i), so r₁=∞ isindicated in Table 3. The second stop S₂ is comprised of a plane r₆, sor₆=∞ is indicated in Table 3. The F number Fno is 2.96.

As Table 3 shows, r₃=∞ and r₄=∞, so the second lens L₂ is anoptical-parallel plate, r₈=∞ and r₉=∞, so the fifth lens L₅ is anoptical-parallel plate, and r₁₂=∞ and r₁₃=∞, so the eighth lens L₈ is anoptical-parallel plate.

Further, r₂ is a positive value and r₅ is a positive value, so the firstlens L₁ is a plano-convex lens where the object side face of this firstlens L₁ is a convex surface facing the object side on a paraxial line,and the third lens L₃ is a plano-convex lens where the image side faceof this third lens L₃ is a convex surface facing the image side on aparaxial line. r₇ is a negative value and r₁₀ is also a negative value,so the fourth lens L₄ is a plano-concave lens where the object side faceof this fourth lens L₄ is a concave surface facing the object side on aparaxial line, and the sixth lens L₆ is a plano-convex lens where theimage side face of this sixth lens L₆ is a convex surface facing theimage side on a paraxial line. r₁₁ is a positive value and r₁₄ is also apositive value, so the seventh lens L₇ is a plano-convex lens where theobject side face of this seventh lens L₇ is a convex surface facing theobject side, and the ninth lens L₉ is a plano-concave lens where theimage side face of this ninth lens L₉ is a concave surface facing theimage side on a paraxial line.

In Embodiment 3, the optical length L with respect to the focal distancef=1.00 mm is 1.137 mm, and the back focus bf is 0.391 mm.

FIG. 12 shows a graph of the distortion aberration curve 3-1, FIG. 13shows a graph of the astigmatism aberration curve (aberration curve 3-2on the meridional surface and aberration curve 3-3 on the sagittalsurface), and FIG. 14 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 3-4 on g-line, aberration curve 3-5 on F-line,aberration curve 3-6 on e-line, aberration curve 3-7 on d-line, andaberration curve 3-8 on C-line).

The ordinates of the aberration curves in FIG. 12 and FIG. 13 show theimage height by a % of the distance from the optical axis. In FIG. 12and FIG. 13, 100% corresponds to 0.631 mm. The ordinate of theaberration curve in FIG. 14 shows the entrance height h (F number), andthe maximum thereof corresponds to 2.96. The abscissa of FIG. 12 showsthe aberration (%), and the abscissa of FIG. 13 and FIG. 14 show thevalue of the aberration (mm).

For the distortion aberration, the absolute value of the aberration is1.52%, which is the maximum, at the position of 100% image height (imageheight: 0.631 mm), and the absolute value of the aberration is within1.52% in a range where the image height is 0.631 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe meridional surface is 0.0147 mm, which is the maximum, at theposition of 80% image height (image height: 0.505 mm), and the absolutevalue of the aberration is within 0.0147 mm in a range where the imageheight is 0.631 mm or less.

For the chromatic/spherical aberration, the absolute value of theaberration curve 3-4 on the g-line is 0.435 mm, which is the maximum, at100% entrance height h, and the absolute value of the aberration iswithin 0.0435 mm.

Therefore according to the imaging lens of Embodiment 3, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcover glass between the imaging lens and the image sensing plane, andgood images can be acquired.

Embodiment 4

Embodiment 4 is an embodiment of the first imaging lens of the presentinvention, wherein the first lens L₁, the third lens L₃, the fourth lensL₄, the sixth lens L₆, the seventh lens L₇ and the ninth lens L₉ areformed of a transparent curable silicone resin SMX-7852 (made by FujiPolymer Industries Co. Ltd.), and the second lens L₂, the fifth lens L₅and the eighth lens L₈ are formed of optical glass BK7 (made by OharaInc.).

The respective composing materials of the first to the ninth lens arethe same as the above mentioned Embodiments 1 and 2, therefore|N₂−N₁|=|N₂−N₃|=|N₅−N₄|=|N₅−N₆|=|N₈−N₇|=|N₈−N₉|=0.00633, which satisfiesthe following Conditions (1), (2), (5), (6), (9) and (10). Also|ν₂−ν₁|=|ν₂−ν₃|=|ν₅−ν₄|=|ν₅−ν₆|=|ν₈−ν₇|=|ν₈−ν₉|=8.0, which satisfies thefollowing Conditions (3), (4), (7), (8), (11) and (12).

FIG. 15 is a cross-sectional view of the imaging lens of Embodiment 4.As FIG. 15 shows, the aperture stop S is formed between the firstjunction type compound lens 14 and the second junction type compoundlens 16. The stop surface of the aperture stop S is a plane, so r₅=∞ isindicated in Table 4. The F number Fno is 3.40.

As Table 4 shows, r₂ is a positive value and r₃ is also a positivevalue, so the second lens L₂ is a meniscus lens of which convex surfaceis facing the object side, r₇ is a negative value and r₈ is also anegative value, so the fifth lens L₅ is a meniscus lens of which convexsurface is facing the image side, and r₁₁ is a positive value and r₁₂ isa negative value, so the eighth lens L₈ is a biconvex lens of which bothside faces are convex surfaces.

r₁ is a positive value, so the first lens L₁ is a lens where the objectside face of this first lens L₁ is a convex surface facing the objectside on a paraxial line. r₄ is a positive value, so the third lens L₃ isa lens where the image side face of this third lens L₃ is a concavesurface facing the image side on a paraxial line.

r₆ is a negative value, so the fourth lens L₄ is a lens where the objectside face of this fourth lens L₄ is a concave surface facing the objectside on a paraxial line. r₉ is a negative value, so the sixth lens L₆ isa lens where the image side face of this sixth lens L₆ is a convexsurface facing the image side on a paraxial line.

r₁₀ is a positive value, so the seventh lens L₇ is a lens where theobject side face of this seventh lens L₇ is a convex surface facing theobject side on a paraxial line. r₁₃ is a positive value, so the ninthlens L₉ is a lens where the image side face of this ninth lens L₉ is aconcave surface facing the image side on a paraxial line.

In Embodiment 4, the optical length L with respect to the focal distancef=1.00 mm is 1.235 mm, and the back focus bf is 0.391 mm.

FIG. 16 shows a graph of the distortion aberration curve 4-1, FIG. 17shows a graph of the astigmatism aberration curve (aberration curve 4-2on the meridional surface and aberration curve 4-3 on the sagittalsurface), and FIG. 18 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 4-4 on g-line, aberration curve 4-5 on F-line,aberration curve 4-6 on e-line, aberration curve 4-7 on d-line, andaberration curve 4-8 on C-line).

The ordinates of the aberration curves in FIG. 16 and FIG. 17 show theimage height by a % of the distance from the optical axis. In FIG. 16and FIG. 17, 100% corresponds to 0.572 mm. The ordinate of theaberration curve in FIG. 18 shows the entrance height h (F number), andthe maximum thereof corresponds to 3.40. The abscissa of FIG. 16 showsthe aberration (%), and the abscissa of FIG. 17 and FIG. 18 show thevalue of the aberration (mm).

For the distortion aberration, the absolute value of the aberration is4.58%, which is the maximum, at the position of 100% image height (imageheight: 0.572 mm), and the absolute value of the aberration is within4.58% in a range where the image height is 0.572 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe sagittal surface is 0.0098 mm, which is the maximum, at the positionof 70% image height (image height: 0.400 mm), and the absolute value ofthe aberration is within 0.0098 mm in a range where the image height is0.572 mm or less. For the chromatic/spherical aberration, the absolutevalue of the aberration curve 4-4 on the g-line is 0.0221 mm, which isthe maximum, at 100% entrance height h, and the absolute value of theaberration is within 0.0221 mm.

Therefore according to the imaging lens of Embodiment 4, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcovering glass between the imaging lens and the image sensing plane, andgood images can be acquired.

Embodiment 5

Embodiment 5 is an embodiment of the second imaging lens of the presentinvention, where the first lens L₁, the third lens L₃, the fourth lensT_(A), the sixth lens L₆, the seventh lens L₇ and the ninth lens L₉ areformed of a transparent curable silicone resin SMX-7852 (made by FujiPolymer Industries Co. Ltd.), and the second lens L₂, the fifth lens L₅and the eighth lens L₈ are formed of optical glass BK7 (made by OharaInc.)

The respective composing materials of the first to the ninth lens arethe same as the above mentioned Embodiments 1, 2 and 4, therefore|N₂−N₁|=|N₂−N₃|=|N₅−N₄|=|N₅−N₆|=|N₈−N₇|=|N₈−N₉|=0.00633, which satisfiesthe following Conditions (1), (2), (5), (6), (9) and (10). Also|ν₂−ν₁|=|ν₂−ν₃|=|ν₅−ν₄|=|ν₅−ν₆|=|ν_(s)−ν₇|=|ν₈−ν₉|=8.0, which satisfiesthe following Conditions (3), (4), (7), (8), (11) and (12).

FIG. 19 is a cross-sectional view of the imaging lens of Embodiment 5.As FIG. 19 shows, the first stop S₁, to play a role of an aperture stop,is formed at a position of an intersection of the first surface (surfaceat the object side) of the first lens L₁ constituting the first junctiontype compound lens 14 and the optical axis. The second stop S₂, to playa role of preventing a flare or smear, is formed between the firstjunction type compound lens 14 and the second junction type compoundlens 16.

The stop surface of the first stop S₁ is a plane r₁, so r₁=∞ isindicated in Table 5. The second stop S₂ is comprised of a plane r₆, sor₆=∞ is indicated in Table 5. The F number Fno is 2.80.

As Table 5 shows, r₃ is a positive value and r₄ is a negative value, sothe second lens L₂ is a biconvex lens of which both side surfaces areconvex surfaces, r₇ is a negative value and r₈ is also a negative value,so the fifth lens L₅ is a meniscus lens of which convex surface isfacing the image side, and r₁₂ is a negative value and r₁₃ is also anegative value, so the eighth lens L₈ is a meniscus lens of which convexsurface is facing the image side.

r₂ is a positive value, so the first lens L₁ is a lens where the objectside face of this first lens L₁ is a convex surface facing the objectside on a paraxial line. r₅ is a negative value, so the third lens L₃ isa lens where the image side face of this third lens L₃ is a convexsurface facing the image side on a paraxial line.

r₇ is a negative value, so the fourth lens L₄ is a lens where the objectside face of this fourth lens L₄ is a concave surface facing the objectside on a paraxial line. r₁₀ is a negative value, so the sixth lens L₆is a lens where the image side face of this sixth lens L₆ is a convexsurface facing the image side on a paraxial line.

r₁₁ is a positive value, so the seventh lens L₇ is a lens where theobject side face of this seventh lens L₇ is a convex r₁₄ is a positivevalue, so the ninth lens L₉ is a lens where the image side face of thisninth lens L₉ is a concave surface facing the image side on a paraxialline.

In Embodiment 5, the optical length L with respect to the focal distancef=1.00 mm is 1.079 mm, and the back focus bf is 0.350 mm.

FIG. 20 shows a graph of the distortion aberration curve 5-1, FIG. 21shows a graph of the astigmatism aberration curve (aberration curve 5-2on the meridional surface and aberration curve 5-3 on the sagittalsurface), and FIG. 22 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 5-4 on g-line, aberration curve 5-5 on F-line,aberration curve 5-6 on e-line, aberration curve 5-7 on d-line, andaberration curve 5-8 on C-line).

The ordinates of the aberration curves in FIG. 20 and FIG. 21 show theimage height by a % of the distance from the optical axis. In FIG. 20and FIG. 21, 100% corresponds to 0.620 mm. The ordinate of theaberration curve in FIG. 22 shows the entrance height h (F number), andthe maximum thereof corresponds to 2.80. The abscissa of FIG. 20 showsthe aberration (%), and the abscissa of FIG. 21 and FIG. 22 show thevalue of the aberration (mm).

For the distortion aberration, the absolute value of the aberration is1.26%, which is the maximum, at the position of 100% image height (imageheight: 0.620 mm), and the absolute value of the aberration is within1.26% in a range where the image height is 0.620 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe meridional surface is 0.0444 mm, which is the maximum, at theposition of 100% image height (image height: 0.620 mm), and the absolutevalue of the aberration is within 0.0444 mm in a range where the imageheight is 0.620 mm or less.

For the chromatic/spherical aberration, the absolute value of theaberration curve 5-4 on the g-line is 0.0416 mm, which is the maximum,at 100% entrance height h, and the absolute value of the aberration iswithin 0.0416 mm.

Therefore according to the imaging lens of Embodiment 5, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcovering glass between the imaging lens and the image sensing plane, andgood images can be acquired.

Embodiment 6

Embodiment 6 is an embodiment of the first imaging lens of the presentinvention, wherein the first lens L₁, the third lens L₃, the fourth lensL₄, the sixth lens L₆, the seventh lens L₇ and the ninth lanes L₉ areformed of a transparent curable silicone resin SMX-7852 (made by FujiPolymer Industries Co. Ltd.), and the second lens L₂, the fifth lens L₅and the eighth lens L₈ are formed of a curable resin material SilplusMHD (made by Nippon Steel Chemical Co. Ltd.).

-   (A) The refractive index N₁ of the first lens L₁ is N₁=1.51000.-   (B) The refractive index N₂ of the second lens L₂ is N₂=1.51100.-   (C) The refractive index N₃ of the third lens L₃ is N₃=1.51000.-   (D) The Abbe number ν₁ of the first lens L₁ is ν₁=56.0.-   (E) The Abbe number ν₂ of the second lens L₂ is ν₂=36.0.-   (F) The Abbe number ν₃ of the third lens L₃ is ν₃=56.0.-   (G) The refractive index N₄ of the fourth lens L₄ is N₄=1.51000.-   (H) The refractive index N₅ of the fifth lens L₅ is N₅=1.51100.-   (I) The refractive index N₆ of the sixth lens L₆ is N₆=1.51000.-   (J) The Abbe number ν₄ of the fourth lens L₄ is ν₄=56.0.-   (K) The Abbe number ν₅ of the fifth lens L₅ is ν₅=36.0.-   (L) The Abbe number ν₆ of the sixth lens L₆ is ν₆=56.0.-   (M) The refractive index N₇ of the seventh lens L₇ is N₇=1.51000.-   (N) The refractive index N₈ of the eighth lens L₈ is N₈=1.51100.-   (O) The refractive index Ng of the ninth lens L₉ is N₉=1.51000.-   (P) The Abbe number ν₇ of the seventh lens L₇ is ν₇=56.0.-   (Q) The Abbe number ν₈ of the eighth lens L₈ is ν₈=36.0.-   (R) The Abbe number ν₉ of the ninth lens L₉ is ν₉=56.0

Therefore |N₂−N₁|=|N₂−N₃|=|N₅−N₄|=|N₅−N₆|=|N₈−N₇|=|N₈−N₉|=0.00100, whichsatisfies the following Conditions (1), (2), (5), (6), (9) and (10).Also |ν₂−ν₁|=|ν₂−ν₃|=|ν₅−ν₄|=|ν₅−ν₆|=|ν₈−ν₇|=|ν₈−ν₉|=20.0, whichsatisfies the following Conditions (3), (4), (7), (8), (11) and (12).

FIG. 23 is a cross-sectional view of the imaging lens of Embodiment 6.As FIG. 23 shows, the aperture stop S is formed between the firstjunction type compound lens 14 and the second junction type compoundlens 16. The stop surface of the aperture stop S is a plane, so r₅=∞ isindicated in Table 6. The F number Fno is 3.40.

As Table 6 shows, r₂=∞ and r₃=∞, so the second lens L₂ is anoptical-parallel plate, r₇=∞ and r₈=∞, so the fifth lens L₅ is anoptical-parallel plate, and r₁₁=∞ and r₁₂=∞, so the eighth lens L₈ is anoptical-parallel plate.

r₁ is a positive value and r₄ is a positive value, so the first lens L₁is a plano-convex lens where the object side face of this first lens L₁is a convex surface facing the object side on a paraxial line, and thethird lens L₃ is a plano-concave lens where the image side face of thisthird lens L₃ is a concave surface facing the image side on a paraxialline. r₆ is a negative value and r₉ is also a negative value, so thefourth lens L₄ is a plano-concave lens where the object side face ofthis fourth lens L₄ is a concave surface facing the object side on aparaxial line, and the sixth lens L₆ is a plano-convex lens where theimage side face of this sixth lens L₆ is a convex surface facing theimage side on a paraxial line. r₁₀ is a positive value and r₁₃ is also apositive value, so the seventh lens L₇ is a plano-convex lens where theobject side face of this seventh lens L₇ is a convex surface facing theobject side, and the ninth lens L₉ is a plano-concave lens where theimage side face of this ninth lens L₉ is a concave surface facing theimage side on a paraxial line.

In Embodiment 6, the optical length L with respect to the focal distancef=1.00 mm is 1.228 mm, and the back focus bf is 0.399 mm.

FIG. 24 shows a graph of the distortion aberration curve 6-1, FIG. 25shows a graph of the astigmatism aberration curve (aberration curve 6-2on the meridional surface and aberration curve 6-3 on the sagittalsurface), and FIG. 26 shows a graph of a chromatic/spherical aberrationcurve (aberration curve 6-4 on g-line, aberration curve 6-5 on F-line,aberration curve 6-6 on e-line, aberration curve 6-7 on d-line, andaberration curve 6-8 on C-line).

The ordinates of the aberration curves in FIG. 24 and FIG. 25 show theimage height by a % of the distance from the optical axis. In FIG. 24and FIG. 25, 100% corresponds to 0.586 mm. The ordinate of theaberration curve in FIG. 26 shows the entrance height h (F number), andthe maximum thereof corresponds to 3.40. The abscissa of FIG. 24 showsthe aberration (%), and the abscissa of FIG. 25 and FIG. 26 show thevalue of the aberration (mm).

For the distortion aberration, the absolute value of the aberration is5.25%, which is the maximum, at the position of 100% image height (imageheight: 0.586 mm), and the absolute value of the aberration is within5.25% in a range where the image height is 0.586 mm or less.

For the astigmatism aberration, the absolute value of the aberration onthe meridional surface is 0.0616 mm, which is the maximum, at theposition of 100% image height (image height: 0.586 mm), and the absolutevalue of the aberration is within 0.0616 mm in a range where the imageheight is 0.586 mm or less.

For the chromatic/spherical aberration, the absolute value of theaberration curve 6-4 on the g-line is 0.0225 mm, which is the maximum,at 100% entrance height h, and the absolute value of the aberration iswithin 0.0225 mm.

Therefore according to the imaging lens of Embodiment 6, the opticallength can be short enough to be installed in a portable telephone, theback focus can be long enough to insert such components as a filter andcovering glass between the imaging lens and the image sensing plane, andgood images can be acquired.

The difference of the imaging lens of Embodiment 6 from the imaginglenses of the above mentioned Embodiment 1 to Embodiment 5 is that thesecond lens L₂, the fifth lens L₅ and the eighth lens L₈ are formed of acurable resin material, that is transparent high hardness siliconeresin. The first junction type compound lens 14 constituting the imaginglens of Embodiment 6 is formed by contacting a liquid type resinmaterial to the second lens L₂ formed of a curable resin material, andsolidifying, that is curing this curable resin material, so that thefirst lens L₁ or the third lens L₃ is bonded to the second lens L₂(direct bonding). The second junction type compound lens 16 is formed bycontacting a liquid type curable resin material to the fifth lens L₅formed of a curable resin material, and solidifying, that is curing thiscurable resin material, so that the fourth lens L₄, or the sixth lens L₆is bonded to the fifth lens L₅ (direct bonding). The third junction typecompound lens 18 is formed by contacting a liquid type curable resinmaterial to the eighth lens L₈ formed of a curable resin material, andsolidifying, that is curing this curable resin material, so that theseventh lens L₇ or the ninth lens L₉ is bonded to the eighth lens L₈(direct bonding).

It is also possible that an optical-parallel plate is formed by acurable resin material, just like the case of the second lens L₂ formedof an optical glass, and using this optical-parallel plate as the secondlens L₂, the first lens L₁, or the third lens L₃ formed of a curableresin material, and this second lens L₂ are indirectly bonded. It isalso possible that an optical-parallel plate is formed of a curableresin material, just like the case of the fifth lens L₅ formed of anoptical glass, using this optical-parallel plate as the fifth lens L₅,and the fourth lens L₄ or the sixth lens L₆ formed of a curable resinmaterial, and this fifth lens L₅, are indirectly bonded. It is alsopossible that an optical-parallel plate is formed of a curable resinmaterial, just like the case of the eighth lens L₈ formed of an opticalglass, and using this optical-parallel plate as the eighth lens L₈, theseventh lens L₇ or the ninth lens L_(g) formed of a curable resinmaterial, and this eighth lens L₈, are indirectly bonded.

As the description on the imaging lenses according to Embodiment 1 toEmbodiment 6 show, the problem to be solved by this invention is solvedby designing each composing lens of the imaging lens so as to satisfythe above Expression (1) to (12). In other words, an imaging lens wherevarious aberrations are well corrected, sufficient back focus isacquired, and optical length is maintained short, can be acquired.

As described above, the imaging lens of the present invention issuitable not only for a lens for a camera built into a portabletelephone, personal computer or digital camera, but also for a lens fora camera built into a personal digital assistant (PDA), a lens for acamera built into a toy having an image recognition function, and a lensfor a camera built into monitoring, inspection or crime preventionequipment.

1. An imaging lens, comprising a first junction type compound lens, anaperture stop, a second junction type compound lens, and a thirdjunction type compound lens, characterized in that said first junctiontype compound lens, said aperture stop, said second junction typecompound lens, and said third junction type compound lens are arrangedin this sequence from an object side to an image side, said firstjunction type compound lens comprises a first lens, a second lens and athird lens arranged in this sequence from the object side to the imageside, said second junction type compound lens comprises a fourth lens, afifth lens and a sixth lens arranged in this sequence from the objectside to the image side, said third junction type compound lens comprisesa seventh lens, an eighth lens and a ninth lens arranged in thissequence from the object side to the image side, said first lens, saidthird lens, said fourth lens, said sixth lens, said seventh lens andsaid ninth lens are formed of a curable resin material, said secondlens, said fifth lens and said eighth lens are formed of a highsoftening temperature optical glass material, said first lens and saidsecond lens are bonded with adhesive, said second lens and said thirdlens are bonded with adhesive, said fourth lens and said fifth lens arebonded with adhesive, said fifth lens and said sixth lens are bondedwith adhesive, said seventh lens and said eighth lens are bonded withadhesive, and said eighth lens and said ninth lens are bonded withadhesive, and the following Conditions (1) to (12) are satisfied:0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦|ν₂−ν₁|≦30.0  (3)0≦|ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦|ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12) where N₁: refractive index of said first lens N₂:refractive index of said second lens N₃: refractive index of said thirdlens ν₁: Abbe number of said first lens ν₂: Abbe number of said secondlens ν₃: Abbe number of said third lens N₄: refractive index of saidfourth lens N₅: refractive index of said fifth lens N₆: refractive indexof said sixth lens ν₄: Abbe number of said fourth lens ν₅: Abbe numberof said fifth lens ν₆: Abbe number of said sixth lens N₇: refractiveindex of said seventh lens N₈: refractive index of said eighth lens N₉:refractive index of said ninth lens ν₇: Abbe number of said seventh lensν₈: Abbe number of said eighth lens ν₉: Abbe number of said ninth lens.2. The imaging lens according to claim 1, characterized in that saidsecond lens is an optical-parallel plate, said first lens is apiano-convex lens where the object side face of said first lens is aconvex surface facing the object side on a paraxial line, said thirdlens is a piano-concave lens where the image side face of said thirdlens is a concave surface facing the image side on a paraxial line, saidfifth lens is an optical-parallel plate, said fourth lens is apiano-concave lens where the object side face of said fourth lens is aconcave surface facing the object side on a paraxial line, said sixthlens is a piano-convex lens where the image side face of said sixth lensis a convex surface facing the image side on a paraxial line, saideighth lens is an optical-parallel plate, said seventh lens is apiano-convex lens where the object side face of said seventh lens is aconvex surface facing the object side on a paraxial line, and said ninthlens is a piano-concave lens where the image side face of said ninthlens is a concave surface facing the image side on a paraxial line. 3.The imaging lens according to claim 1, characterized in that said secondlens is a meniscus lens of which convex surface faces the object side,said first lens is a lens where the object side face of said first lensis a convex surface facing the object side on a paraxial line, saidthird lens is a lens where the image side face of said third lens is aconcave surface facing the image side on a paraxial line, said fifthlens is a meniscus lens of which convex surface faces the image side,said fourth lens is a lens where the object side face of said fourthlens is a concave surface facing the object side on a paraxial line,said sixth lens is a lens where the image side face of said sixth lensis a convex surface facing the image side on a paraxial line, saideighth lens is a biconvex lens of which both side faces are convexsurfaces, said seventh lens is a lens where the object side face of saidseventh lens is a convex surface facing the object side on a paraxialline, and said ninth lens is a lens where the image side face of saidninth lens is a concave surface facing the image side on a paraxialline.
 4. The imaging lens according to claim 1, characterized in thatthe object side face of said first lens, the image side face of saidthird lens, the object side face of said fourth lens, the image sideface of said sixth lens, the object side face of said seventh lens, andthe image side face of said ninth lens are aspherical.
 5. The imaginglens according to claim 1, characterized in that both surfaces of saidsecond lens, both surfaces of said fifth lens, and both surfaces of saideight lens, a total of six surfaces, are coating-processed.
 6. Theimaging lens according to claim 1, characterized in that said curableresin material is a transparent curable silicone resin.
 7. An imaginglens, comprising an aperture stop (first stop), a first junction typecompound lens, a second stop, a second junction type compound lens, anda third junction type compound lens, characterized in that said aperturestop, said first junction type compound lens, said second stop, saidsecond junction type compound lens, and said third junction typecompound lens are arranged in this sequence from an object side to animage side, said first junction type compound lens comprises a firstlens, a second lens, and a third lens arranged in this sequence from theobject side to the image side, said second junction type compound lenscomprises a fourth lens, a fifth lens and a sixth lens arranged in thissequence from the object side to the image side, said third junctiontype compound lens comprises a seventh lens, an eighth lens and a ninthlens arranged in this sequence from the object side to the image side,said first lens, said third lens, said fourth lens, said sixth lens,said seventh lens and said ninth lens are formed of a curable resinmaterial, said second lens, said fifth lens and said eighth lens areformed of a high softening temperature optical glass material, saidfirst lens and said second lens are bonded with adhesive, said secondlens and said third lens are bonded with adhesive, said fourth lens andsaid fifth lens are bonded with adhesive, said fifth lens and said sixthlens are bonded with adhesive, said seventh lens and said eighth lensare bonded with adhesive, and said eighth lens and said ninth lens arebonded with adhesive, and the following Conditions (1) to (12) aresatisfied:0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦|ν₂−ν₁|≦30.0  (3)0≦|ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦|ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12) where N₁: refractive index of said first lens N₂:refractive index of said second lens N₃: refractive index of said thirdlens ν₁: Abbe number of said first lens ν₂: Abbe number of said secondlens ν₃: Abbe number of said third lens N₄: refractive index of saidfourth lens N₅: refractive index of said fifth lens N₆: refractive indexof said sixth lens ν₄: Abbe number of said fourth lens ν₅: Abbe numberof said fifth lens ν₆: Abbe number of said sixth lens N₇: refractiveindex of said seventh lens N₈: refractive index of said eighth lens N₉:refractive index of said ninth lens ν₇: Abbe number of said seventh lensν₈: Abbe number of said eighth lens ν₉: Abbe number of said ninth lens.8. The imaging lens according to claim 7, characterized in that saidsecond lens is an optical-parallel plate, said first lens is apiano-convex lens where the object side face of said first lens is aconvex surface facing the object side on a paraxial line, said thirdlens is a piano-convex lens where the image side face of said third lensis a convex surface facing the image side on a paraxial line, said fifthlens is an optical-parallel plate, said fourth lens is a piano-concavelens where the object side face of said fourth lens is a concave surfacefacing the object side on a paraxial line, said sixth lens is apiano-convex lens where the image side face of said sixth lens is aconvex surface facing the image side on a paraxial line, said eighthlens is an optical-parallel plate, said seventh lens is a piano-convexlens where the object side face of said seventh lens is a convex surfacefacing the object side on a paraxial line, and said ninth lens is apiano-concave lens where the image side face of said ninth lens is aconcave surface facing the image side on a paraxial line.
 9. The imaginglens according to claim 7, characterized in that said second lens is abiconvex lens of which both side faces are convex surfaces, said firstlens is a lens where the object side face of said first lens is a convexsurface facing the object side on a paraxial line, said third lens is alens where the image side face of said third lens is a convex surfacefacing the image side on a paraxial line, said fifth lens is a meniscuslens of which convex surface faces the image side, said fourth lens is alens where the object side face of said fourth lens is a concave surfacefacing the object side on a paraxial line, said sixth lens is a lenswhere the image side face of said sixth lens is a convex surface facingthe image side on a paraxial line, said eighth lens is a meniscus lensof which convex surface faces the image side, said seventh lens is alens where the object side face of said seventh lens is a convex surfacefacing the object side on a paraxial line, and said ninth lens is a lenswhere the image side face of said ninth lens is a concave surface facingthe image side on a paraxial line.
 10. The imaging lens according toclaim 7, characterized in that the object side face of said first lens,the image side face of said third lens, the object side face of saidfourth lens, the image side face of said sixth lens, the object sideface of said seventh lens, and the image side face of said ninth lensare aspherical.
 11. The imaging lens according to claim 7, characterizedin that both surfaces of said second lens, both surfaces of said fifthlens, and both surfaces of said eight lens, a total of six surfaces, arecoating-processed.
 12. The imaging lens according to claim 7,characterized in that said curable resin material is a transparentcurable silicone resin.
 13. An imaging lens, comprising a first junctiontype compound lens, an aperture stop, a second junction type compoundlens, and a third junction type compound lens, characterized in thatsaid first junction type compound lens, said aperture stop, said secondjunction type compound lens, and said third junction type compound lensare arranged in this sequence from an object side to an image side, saidfirst junction type compound lens comprises a first lens, a second lensand a third lens arranged in this sequence from the object side to theimage side, said second junction type compound lens comprises a fourthlens, a fifth lens and a sixth lens arranged in this sequence from theobject side to the image side, said third junction type compound lenscomprises a seventh lens, an eighth lens and a ninth lens arranged inthis sequence from the object side to the image side, said first lens,said second lens, said third lens, said fourth lens, said fifth lens,said sixth lens, said seventh lens, said eighth lens and said ninth lensare formed of a curable resin material, said first lens and said secondlens are directly bonded, said second lens and said third lens aredirectly bonded, said fourth lens and said fifth lens are directlybonded, said fifth lens and said sixth lens are directly bonded, saidseventh lens and said eighth lens are directly bonded, and said eighthlens and said ninth lens are directly bonded, and the followingConditions (1) to (12) are satisfied:0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦|ν₂−ν₁|≦30.0  (3)0≦|ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦|ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12) where N₁: refractive index of said first lens N₂:refractive index of said second lens N₃: refractive index of said thirdlens ν₁: Abbe number of said first lens ν₂: Abbe number of said secondlens ν₃: Abbe number of said third lens N₄: refractive index of saidfourth lens N₅: refractive index of said fifth lens N₆: refractive indexof said sixth lens ν₄: Abbe number of said fourth lens ν₅: Abbe numberof said fifth lens ν₆: Abbe number of said sixth lens N₇: refractiveindex of said seventh lens N₈: refractive index of said eighth lens N₉:refractive index of said ninth lens ν₇: Abbe number of said seventh lensν₈: Abbe number of said eighth lens ν₉: Abbe number of said ninth lens.14. The imaging lens according to claim 13, characterized in that saidsecond lens is an optical-parallel plate, said first lens is apiano-convex lens where the object side face of said first lens is aconvex surface facing the object side on a paraxial line, said thirdlens is a piano-concave lens where the image side face of said thirdlens is a concave surface facing the image side on a paraxial line, saidfifth lens is an optical-parallel plate, said fourth lens is apiano-concave lens where the object side face of said fourth lens is aconcave surface facing the object side on a paraxial line, said sixthlens is a piano-convex lens where the image side face of said sixth lensis a convex surface facing the image side on a paraxial line, saideighth lens is an optical-parallel plate, said seventh lens is apiano-convex lens where the object side face of said seventh lens is aconvex surface facing the object side on a paraxial line, and said ninthlens is a piano-concave lens where the image side face of said ninthlens is a concave surface facing the image side on a paraxial line. 15.The imaging lens according to claim 13, characterized in that the objectside face of said first lens, the image side face of said third lens,the object side face of said fourth lens, the image side face of saidsixth lens, the object side face of said seventh lens, and the imageside face of said ninth lens are aspherical.
 16. The imaging lensaccording to claim 13, characterized in that said curable resin materialis a transparent curable silicone resin.
 17. An imaging lens, comprisinga first junction type compound lens, an aperture stop, a second junctiontype compound lens, a third junction type compound lens, characterizedin that said first junction type compound lens, said aperture stop, saidsecond junction type compound lens, and said third junction typecompound lens are arranged in this sequence from an object side to animage side, said first junction type compound lens comprises a firstlens, a second lens and a third lens arranged in this sequence from theobject side to the image side, said second junction type compound lenscomprises a fourth lens, a fifth lens and a sixth lens arranged in thissequence from the object side to the image side, said third junctiontype compound lens comprises a seventh lens, an eighth lens and a ninthlens arranged in this sequence from the object side to the image side,said first lens, said second lens, said third lens, said fourth lens,said fifth lens, said sixth lens, said seventh lens, said eighth lensand said ninth lens are formed of a curable resin material, said firstlens and said second lens are bonded with adhesive, said second lens andsaid third lens are bonded with adhesive, said fourth lens and saidfifth lens are bonded with adhesive, said fifth lens and said sixth lensare bonded with adhesive, said seventh lens and said eighth lens arebonded with adhesive, and said eighth lens and said ninth lens arebonded with adhesive, and the following Conditions (1) to (12) aresatisfied:0≦|N ₂ −N ₁|≦0.1  (1)0≦|N ₂ −N ₃|≦0.1  (2)0≦|ν₂−ν₁|≦30.0  (3)0≦|ν₂−ν₃|≦30.0  (4)0≦|N ₅ −N ₄|≦0.1  (5)0≦|N ₅ −N ₆|≦0.1  (6)0≦|ν₅−ν₄|≦30.0  (7)0≦|ν₅−ν₆|≦30.0  (8)0≦|N ₈ −N ₇|≦0.1  (9)0≦|N ₈ −N ₉|≦0.1  (10)0≦|ν₈−ν₇|≦30.0  (11)0≦|ν₈−ν₉|≦30.0  (12) where N₁: refractive index of said first lens N₂:refractive index of said second lens N₃: refractive index of said thirdlens ν₁: Abbe number of said first lens ν₂: Abbe number of said secondlens ν₃: Abbe number of said third lens N₄: refractive index of saidfourth lens N₅: refractive index of said fifth lens N₆: refractive indexof said sixth lens ν₄: Abbe number of said fourth lens ν₅: Abbe numberof said fifth lens ν₆: Abbe number of said sixth lens N₇: refractiveindex of said seventh lens N₈: refractive index of said eighth lens N₉:refractive index of said ninth lens ν₇: Abbe number of said seventh lensν₈: Abbe number of said eighth lens ν₉: Abbe number of said ninth lens.18. The imaging lens according to claim 17, characterized in that saidsecond lens is an optical-parallel plate, said first lens is apiano-convex lens where the object side face of said first lens is aconvex surface facing the object side on a paraxial line, said thirdlens is a piano-concave lens where the image side face of said thirdlens is a concave surface facing the image side on a paraxial line, saidfifth lens is an optical-parallel plate, said fourth lens is apiano-concave lens where the object side face of said fourth lens is aconcave surface facing the object side on a paraxial line, said sixthlens is a piano-convex lens where the image side face of said sixth lensis a convex surface facing the image side on a paraxial line, saideighth lens is an optical-parallel plate, said seventh lens is apiano-convex lens where the object side face of said seventh lens is aconvex surface facing the object side on a paraxial line, and said ninthlens is a piano-concave lens where the image side face of said ninthlens is a concave surface facing the image side on a paraxial line. 19.The imaging lens according to claim 17, characterized in that the objectside face of said first lens, the image side face of said third lens,the object side face of said fourth lens, the image side face of saidsixth lens, the object side face of said seventh lens, and the imageside face of said ninth lens are aspherical.
 20. The imaging lensaccording to claim 17, characterized in that both surfaces of saidsecond lens, both surfaces of said fifth lens, and both surfaces of saideight lens, a total of six surfaces, are coating-processed.
 21. Theimaging lens according to claim 17, characterized in that said curableresin material is a transparent curable silicone resin.